🐛 [firebase_database] FirebaseDatabase.instance.ref() crashes on iOS if empty path in ref()

Bug report

Describe the bug

Calling .ref().update() with an empty path in .ref() crashes on iOS. If i call .ref("test").update() it doesn't crash.

Note : this seems to only happens when writing data, not when listening and only on iOS.

Moreover, the old reference() deprecated method in 9.0.0 is also crashing on iOS :/

Steps to reproduce

Steps to reproduce the behavior:

Run the sample code
See that the app crashes

Expected behavior

I expect the app to not crash and use the "/" as root database path when calling .ref().

Sample project

import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_database/firebase_database.dart';
import 'package:flutter/material.dart';

Future<void> main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(const TestApp());
}

class TestApp extends StatelessWidget {
  const TestApp({Key? key}) : super(key: key);

  void crash() {
    FirebaseDatabase.instance.ref().update({"test": "crash test"});
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: GestureDetector(
            onTap: () {
              crash();
            },
            child: Container(
              width: 200,
              height: 200,
              color: Colors.blue,
              child: const Center(child: Text("Crash me !", style: TextStyle(fontSize: 20, color: Colors.white),)),
            ),
          ),
        ),
      ),
    );
  }
}

Logs

*** Terminating app due to uncaught exception ‘InvalidPathValidation’, reason: ‘(referenceWithPath) Must be a non-empty string and not contain ‘.’ ‘#’ ‘$’ ‘[’ or ‘]’'
*** First throw call stack:
(0x1841ae04c 0x19c822f54 0x1088586fc 0x1088588a0 0x1087f0a0c 0x104acd464 0x104acac60 0x104ac9b1c 0x10bcbd7f8 0x10b809f00 0x10bb155f0 0x10baba39c 0x10babd994 0x1841c3268 0x184147c40 0x18414243c 0x184120c58 0x1841343b8 0x19fac438c 0x186ad46a8 0x1868537f4 0x10419cd5c 0x1077b5a24)
libc++abi: terminating with uncaught exception of type NSException
* thread #1, queue = ‘com.apple.main-thread’, stop reason = signal SIGABRT
    frame #0: 0x00000001ba57b964 libsystem_kernel.dylib`__pthread_kill + 8
libsystem_kernel.dylib`__pthread_kill:
->  0x1ba57b964 <+8>:  b.lo   0x1ba57b984               ; <+40>
    0x1ba57b968 <+12>: pacibsp
    0x1ba57b96c <+16>: stp    x29, x30, [sp, #-0x10]!
    0x1ba57b970 <+20>: mov    x29, sp
Target 0: (Runner) stopped.

Flutter doctor

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``` [✓] Flutter (Channel stable, 2.5.3, on macOS 12.0.1 21A559 darwin-x64, locale fr-FR) [✓] Android toolchain - develop for Android devices (Android SDK version 31.0.0) [✓] Xcode - develop for iOS and macOS [✓] Chrome - develop for the web [✓] Android Studio (version 2020.3) [✓] VS Code (version 1.62.3) [✓] Connected device (3 available) • No issues found! ```

Flutter dependencies

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``` Dart SDK 2.14.4 Flutter SDK 2.5.3 myappname 1.0.0+1 dependencies: - app_settings 4.1.1 [flutter] - app_tracking_transparency 2.0.2+1 [flutter] - apple_maps_flutter 1.0.1 [flutter] - auto_size_text 3.0.0 [flutter] - badges 2.0.2 [flutter] - cached_network_image 3.2.0 [flutter flutter_cache_manager octo_image cached_network_image_platform_interface cached_network_image_web] - camera 0.9.4+5 [camera_platform_interface camera_web flutter pedantic quiver flutter_plugin_android_lifecycle] - clipboard 0.1.3 [flutter] - cloud_functions 3.2.2 [cloud_functions_platform_interface cloud_functions_web firebase_core firebase_core_platform_interface flutter] - connectivity_plus 2.1.0 [flutter connectivity_plus_platform_interface connectivity_plus_linux connectivity_plus_macos connectivity_plus_web connectivity_plus_windows] - country_code_picker 2.0.2 [flutter modal_bottom_sheet collection universal_platform] - crypto 3.0.1 [collection typed_data] - cupertino_back_gesture 0.1.0 [flutter] - cupertino_icons 1.0.4 - disk_space 0.2.1 [flutter] - emoji_picker_flutter 1.0.8 [flutter shared_preferences] - extended_image 5.1.3 [extended_image_library flutter meta] - extended_tabs 2.3.0 [flutter] - firebase_analytics 9.0.1 [firebase_analytics_platform_interface firebase_analytics_web firebase_core firebase_core_platform_interface flutter] - firebase_auth 3.3.2 [firebase_auth_platform_interface firebase_auth_web firebase_core firebase_core_platform_interface flutter meta] - firebase_core 1.10.4 [firebase_core_platform_interface firebase_core_web flutter meta] - firebase_crashlytics 2.4.2 [firebase_core firebase_core_platform_interface firebase_crashlytics_platform_interface flutter stack_trace] - firebase_database 9.0.1 [firebase_core firebase_core_platform_interface firebase_database_platform_interface firebase_database_web flutter] - firebase_dynamic_links 4.0.1 [firebase_core firebase_core_platform_interface firebase_dynamic_links_platform_interface flutter meta plugin_platform_interface] - firebase_messaging 11.2.2 [firebase_core firebase_core_platform_interface firebase_messaging_platform_interface firebase_messaging_web flutter meta] - firebase_performance 0.8.0+1 [firebase_core firebase_core_platform_interface firebase_performance_platform_interface firebase_performance_web flutter] - firebase_storage 10.2.2 [firebase_core firebase_core_platform_interface firebase_storage_platform_interface firebase_storage_web flutter] - flutter 0.0.0 [characters collection meta typed_data vector_math sky_engine] - flutter_app_badger 1.3.0 [flutter] - flutter_arc_text 0.5.0 [characters flutter] - flutter_contacts 1.1.1+2 [flutter] - flutter_facebook_auth 3.5.6+3 [flutter flutter_facebook_auth_platform_interface flutter_facebook_auth_web] - flutter_ffmpeg 0.4.2 [flutter] - flutter_image_compress 1.1.0 [flutter] - flutter_localizations 0.0.0 [flutter intl characters clock collection meta path typed_data vector_math] - flutter_native_text_input 1.2.2 [flutter] - flutter_sound_lite 8.4.2 [path_provider recase uuid provider path synchronized logger flutter flutter_sound_platform_interface flutter_sound_web] - flutter_staggered_grid_view 0.5.0-dev.1 [flutter] - flutter_svg 1.0.0 [flutter meta path_drawing vector_math xml] - geocoding 2.0.1 [flutter geocoding_platform_interface] - geolocator 8.0.0 [flutter geolocator_platform_interface geolocator_android geolocator_apple geolocator_web] - google_fonts 2.1.0 [flutter http path_provider crypto] - google_maps_flutter 2.1.1 [flutter flutter_plugin_android_lifecycle google_maps_flutter_platform_interface] - google_mobile_ads 1.0.1 [meta flutter] - google_sign_in 5.2.1 [flutter google_sign_in_platform_interface google_sign_in_web meta] - hive 2.0.4 [meta crypto] - hive_flutter 1.1.0 [flutter hive path_provider path] - http 0.13.4 [async http_parser meta path] - image_editor 1.0.2 [flutter] - in_app_review 2.0.3 [flutter in_app_review_platform_interface] - intl 0.17.0 [clock path] - logger 1.1.0 - native_admob_flutter 1.5.0 [flutter] - package_info_plus 1.3.0 [flutter package_info_plus_platform_interface package_info_plus_linux package_info_plus_macos package_info_plus_windows package_info_plus_web] - path 1.8.0 - path_provider 2.0.7 [flutter path_provider_android path_provider_ios path_provider_linux path_provider_macos path_provider_platform_interface path_provider_windows] - percent_indicator 3.4.0 [flutter] - perfect_volume_control 1.0.5 [flutter] - permission_handler 8.3.0 [flutter meta permission_handler_platform_interface] - photo_manager 1.3.10 [flutter] - provider 6.0.1 [collection flutter nested] - pull_to_refresh 2.0.0 [flutter] - rive 0.7.33 [collection flutter graphs http meta] - scrollable_positioned_list 0.2.3 [flutter collection] - share_plus 3.0.4 [meta mime flutter share_plus_platform_interface share_plus_linux share_plus_macos share_plus_windows share_plus_web] - shared_preferences 2.0.9 [flutter meta shared_preferences_android shared_preferences_ios shared_preferences_linux shared_preferences_macos shared_preferences_platform_interface shared_preferences_web shared_preferences_windows] - sign_in_with_apple 3.3.0 [flutter meta sign_in_with_apple_platform_interface sign_in_with_apple_web] - sliver_tools 0.2.5 [flutter] - sqflite 2.0.1 [flutter sqflite_common path] - translator 0.1.7 [http] - url_launcher 6.0.17 [flutter meta url_launcher_android url_launcher_ios url_launcher_linux url_launcher_macos url_launcher_platform_interface url_launcher_web url_launcher_windows] - uuid 3.0.5 [crypto] - video_compress 3.1.1 [flutter] - video_player 2.2.7 [flutter meta video_player_platform_interface video_player_web html] - video_thumbnail 0.4.3 [flutter] - visibility_detector 0.2.2 [flutter] dev dependencies: - build_runner 2.1.5 [args async analyzer build build_config build_daemon build_resolvers build_runner_core code_builder collection crypto dart_style frontend_server_client glob graphs http_multi_server io js logging meta mime package_config path pool pub_semver pubspec_parse shelf shelf_web_socket stack_trace stream_transform timing watcher web_socket_channel yaml] - flutter_lints 1.0.4 [lints] - flutter_test 0.0.0 [flutter test_api path fake_async clock stack_trace vector_math async boolean_selector characters charcode collection matcher meta source_span stream_channel string_scanner term_glyph typed_data] - hive_generator 1.1.1 [build source_gen hive analyzer source_helper] transitive dependencies: - _fe_analyzer_shared 31.0.0 [meta] - analyzer 2.8.0 [_fe_analyzer_shared cli_util collection convert crypto glob meta package_config path pub_semver source_span watcher yaml] - args 2.3.0 - async 2.8.1 [collection meta] - boolean_selector 2.1.0 [source_span string_scanner] - build 2.1.1 [analyzer async convert crypto glob logging meta path] - build_config 1.0.0 [checked_yaml json_annotation path pubspec_parse yaml] - build_daemon 3.0.1 [built_collection built_value http_multi_server logging path pool shelf shelf_web_socket stream_transform watcher web_socket_channel] - build_resolvers 2.0.5 [analyzer async build crypto graphs logging path package_config pool pub_semver stream_transform yaml] - build_runner_core 7.2.2 [async build build_config build_resolvers collection convert crypto glob graphs json_annotation logging meta path package_config pool timing watcher yaml] - built_collection 5.1.1 - built_value 8.1.3 [built_collection collection fixnum meta] - cached_network_image_platform_interface 1.0.0 [flutter flutter_cache_manager] - cached_network_image_web 1.0.1 [flutter flutter_cache_manager cached_network_image_platform_interface] - camera_platform_interface 2.1.1 [cross_file flutter meta plugin_platform_interface stream_transform] - camera_web 0.2.1+1 [camera_platform_interface flutter flutter_web_plugins stream_transform] - characters 1.1.0 - charcode 1.3.1 - checked_yaml 2.0.1 [json_annotation source_span yaml] - cli_util 0.3.5 [meta path] - clock 1.1.0 - cloud_functions_platform_interface 5.0.17 [firebase_core flutter meta plugin_platform_interface] - cloud_functions_web 4.2.3 [cloud_functions_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins js] - code_builder 4.1.0 [built_collection built_value collection matcher meta] - collection 1.15.0 - connectivity_plus_linux 1.1.1 [flutter connectivity_plus_platform_interface meta nm] - connectivity_plus_macos 1.2.1 [connectivity_plus_platform_interface flutter] - connectivity_plus_platform_interface 1.1.1 [flutter meta plugin_platform_interface] - connectivity_plus_web 1.1.0+1 [connectivity_plus_platform_interface flutter_web_plugins flutter] - connectivity_plus_windows 1.2.0 [connectivity_plus_platform_interface flutter] - convert 3.0.1 [typed_data] - cross_file 0.3.2 [flutter js meta] - csslib 0.17.1 [source_span] - dart_style 2.2.0 [analyzer args path pub_semver source_span] - dbus 0.6.6 [args ffi meta xml] - extended_image_library 3.1.0 [crypto flutter http_client_helper path path_provider] - fake_async 1.2.0 [clock collection] - ffi 1.1.2 - file 6.1.2 [meta path] - firebase 9.0.2 [http http_parser js] - firebase_analytics_platform_interface 3.0.1 [firebase_core flutter meta plugin_platform_interface] - firebase_analytics_web 0.4.0+1 [firebase_analytics_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins js] - firebase_auth_platform_interface 6.1.7 [firebase_core flutter meta plugin_platform_interface] - firebase_auth_web 3.3.3 [firebase_auth_platform_interface firebase_core firebase_core_web flutter flutter_web_plugins http_parser intl js meta] - firebase_core_platform_interface 4.2.1 [collection flutter meta plugin_platform_interface] - firebase_core_web 1.5.1 [firebase_core_platform_interface flutter flutter_web_plugins js meta] - firebase_crashlytics_platform_interface 3.1.9 [collection firebase_core flutter meta plugin_platform_interface] - firebase_database_platform_interface 0.2.0+1 [collection firebase_core flutter meta plugin_platform_interface] - firebase_database_web 0.2.0+1 [firebase_core firebase_core_web firebase_database_platform_interface flutter flutter_web_plugins js] - firebase_dynamic_links_platform_interface 0.2.0+1 [firebase_core flutter meta plugin_platform_interface] - firebase_messaging_platform_interface 3.1.2 [firebase_core flutter meta plugin_platform_interface] - firebase_messaging_web 2.2.3 [firebase_core firebase_core_web firebase_messaging_platform_interface flutter flutter_web_plugins js meta] - firebase_performance_platform_interface 0.1.0+1 [firebase_core flutter plugin_platform_interface] - firebase_performance_web 0.1.0+1 [firebase firebase_core firebase_core_web firebase_performance_platform_interface flutter flutter_web_plugins js] - firebase_storage_platform_interface 4.0.9 [collection firebase_core flutter meta plugin_platform_interface] - firebase_storage_web 3.2.3 [async firebase_core firebase_core_web firebase_storage_platform_interface flutter flutter_web_plugins http js meta] - fixnum 1.0.0 - flutter_blurhash 0.6.0 [flutter meta pedantic] - flutter_cache_manager 3.3.0 [clock collection file flutter http path path_provider pedantic rxdart sqflite uuid] - flutter_facebook_auth_platform_interface 2.7.0 [flutter plugin_platform_interface] - flutter_facebook_auth_web 2.6.0+2 [flutter flutter_web_plugins js flutter_facebook_auth_platform_interface] - flutter_plugin_android_lifecycle 2.0.5 [flutter] - flutter_sound_platform_interface 8.4.2 [flutter meta plugin_platform_interface logger] - flutter_sound_web 8.4.2 [flutter_sound_platform_interface flutter logger flutter_web_plugins meta js] - flutter_web_plugins 0.0.0 [flutter js characters collection meta typed_data vector_math] - frontend_server_client 2.1.2 [async path] - geocoding_platform_interface 2.0.1 [flutter meta plugin_platform_interface] - geolocator_android 3.0.0+4 [flutter geolocator_platform_interface] - geolocator_apple 2.0.0+2 [flutter geolocator_platform_interface] - geolocator_platform_interface 3.0.0+1 [flutter plugin_platform_interface vector_math meta] - geolocator_web 2.1.0 [flutter flutter_web_plugins geolocator_platform_interface] - glob 2.0.2 [async collection file path string_scanner] - google_maps_flutter_platform_interface 2.1.3 [collection flutter meta plugin_platform_interface stream_transform] - google_sign_in_platform_interface 2.1.0 [flutter meta quiver] - google_sign_in_web 0.10.0+3 [flutter flutter_web_plugins google_sign_in_platform_interface js meta] - graphs 2.1.0 [collection] - html 0.15.0 [csslib source_span] - http_client_helper 2.0.2 [http] - http_multi_server 3.0.1 [async] - http_parser 4.0.0 [charcode collection source_span string_scanner typed_data] - in_app_review_platform_interface 2.0.2 [flutter url_launcher plugin_platform_interface platform] - io 1.0.3 [meta path string_scanner] - js 0.6.3 - json_annotation 4.4.0 [meta] - lints 1.0.1 - logging 1.0.2 - matcher 0.12.10 [stack_trace] - meta 1.7.0 - mime 1.0.1 - modal_bottom_sheet 2.0.0 [flutter] - nested 1.0.0 [flutter] - nm 0.4.1 [dbus] - octo_image 1.0.1 [flutter flutter_blurhash] - package_config 2.0.2 [path] - package_info_plus_linux 1.0.3 [package_info_plus_platform_interface flutter path] - package_info_plus_macos 1.3.0 [flutter] - package_info_plus_platform_interface 1.0.2 [flutter meta plugin_platform_interface] - package_info_plus_web 1.0.4 [flutter flutter_web_plugins http meta package_info_plus_platform_interface] - package_info_plus_windows 1.0.4 [package_info_plus_platform_interface ffi flutter win32] - path_drawing 1.0.0 [vector_math meta path_parsing flutter] - path_parsing 1.0.0 [vector_math meta] - path_provider_android 2.0.9 [flutter path_provider_platform_interface] - path_provider_ios 2.0.7 [flutter path_provider_platform_interface] - path_provider_linux 2.1.2 [flutter path path_provider_platform_interface xdg_directories] - path_provider_macos 2.0.4 [flutter meta path_provider_platform_interface] - path_provider_platform_interface 2.0.1 [flutter meta platform plugin_platform_interface] - path_provider_windows 2.0.4 [ffi flutter meta path path_provider_platform_interface win32] - pedantic 1.11.1 - permission_handler_platform_interface 3.7.0 [flutter meta plugin_platform_interface] - petitparser 4.4.0 [meta] - platform 3.1.0 - plugin_platform_interface 2.0.2 [meta] - pool 1.5.0 [async stack_trace] - process 4.2.4 [file path platform] - pub_semver 2.1.0 [collection meta] - pubspec_parse 1.2.0 [checked_yaml collection json_annotation pub_semver yaml] - quiver 3.0.1+1 [matcher] - recase 4.0.0 - rxdart 0.27.3 - share_plus_linux 2.0.4 [share_plus_platform_interface file flutter meta url_launcher] - share_plus_macos 2.0.2 [share_plus_platform_interface flutter] - share_plus_platform_interface 2.0.1 [flutter meta mime plugin_platform_interface] - share_plus_web 2.0.4 [share_plus_platform_interface url_launcher flutter flutter_web_plugins meta] - share_plus_windows 2.0.3 [share_plus_platform_interface flutter meta url_launcher] - shared_preferences_android 2.0.9 [flutter meta shared_preferences_platform_interface] - shared_preferences_ios 2.0.8 [flutter meta shared_preferences_platform_interface] - shared_preferences_linux 2.0.3 [file flutter meta path path_provider_linux shared_preferences_platform_interface] - shared_preferences_macos 2.0.2 [flutter shared_preferences_platform_interface] - shared_preferences_platform_interface 2.0.0 [flutter] - shared_preferences_web 2.0.2 [flutter flutter_web_plugins meta shared_preferences_platform_interface] - shared_preferences_windows 2.0.3 [file flutter meta path path_provider_platform_interface path_provider_windows shared_preferences_platform_interface] - shelf 1.2.0 [async collection http_parser path stack_trace stream_channel] - shelf_web_socket 1.0.1 [shelf stream_channel web_socket_channel] - sign_in_with_apple_platform_interface 1.0.0 [flutter plugin_platform_interface meta] - sign_in_with_apple_web 1.0.1 [flutter flutter_web_plugins sign_in_with_apple_platform_interface js] - sky_engine 0.0.99 - source_gen 1.2.0 [analyzer async build dart_style glob meta path source_span yaml] - source_helper 1.3.0 [analyzer collection source_gen] - source_span 1.8.1 [collection path term_glyph] - sqflite_common 2.0.1+1 [synchronized path meta] - stack_trace 1.10.0 [path] - stream_channel 2.1.0 [async] - stream_transform 2.0.0 - string_scanner 1.1.0 [charcode source_span] - synchronized 3.0.0 - term_glyph 1.2.0 - test_api 0.4.2 [async boolean_selector collection meta source_span stack_trace stream_channel string_scanner term_glyph matcher] - timing 1.0.0 [json_annotation] - typed_data 1.3.0 [collection] - universal_platform 1.0.0+1 - url_launcher_android 6.0.13 [flutter meta url_launcher_platform_interface] - url_launcher_ios 6.0.13 [flutter meta url_launcher_platform_interface] - url_launcher_linux 2.0.2 [flutter] - url_launcher_macos 2.0.2 [flutter] - url_launcher_platform_interface 2.0.4 [flutter plugin_platform_interface] - url_launcher_web 2.0.5 [flutter flutter_web_plugins meta url_launcher_platform_interface] - url_launcher_windows 2.0.2 [flutter] - vector_math 2.1.0 - video_player_platform_interface 4.2.0 [flutter flutter_test meta] - video_player_web 2.0.4 [flutter flutter_web_plugins meta video_player_platform_interface] - watcher 1.0.1 [async path] - web_socket_channel 2.1.0 [async crypto stream_channel] - win32 2.3.1 [ffi] - xdg_directories 0.2.0 [meta path process] - xml 5.3.1 [collection meta petitparser] - yaml 3.1.0 [collection source_span string_scanner] ```

firebase / flutterfire