[BUG]: Error Widget

[Kimiblock]

Null check operator used on a null value
#0      SelectableRegionState.endGlyphHeight (package:flutter/src/widgets/selectable_region.dart:1304)
#1      SelectableRegionState.contextMenuAnchors (package:flutter/src/widgets/selectable_region.dart:1144)
#2      new AdaptiveTextSelectionToolbar.selectableRegion (package:flutter/src/material/adaptive_text_selection_toolbar.dart:179)
#3      SelectionArea._defaultContextMenuBuilder (package:flutter/src/material/selection_area.dart:96)
#4      SelectableRegionState._onAnyDragEnd.<anonymous closure> (package:flutter/src/widgets/selectable_region.dart:736)
#5      SelectionOverlay.showToolbar.<anonymous closure> (package:flutter/src/widgets/text_selection.dart:1436)
#6      ContextMenuController.show.<anonymous closure> (package:flutter/src/widgets/context_menu_controller.dart:65)
#7      _OverlayEntryWidgetState.build (package:flutter/src/widgets/overlay.dart:398)
#8      StatefulElement.build (package:flutter/src/widgets/framework.dart:5599)
#9      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5487)
#10     StatefulElement.performRebuild (package:flutter/src/widgets/framework.dart:5650)
#11     Element.rebuild (package:flutter/src/widgets/framework.dart:5203)
#12     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:2905)
#13     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:1136)
#14     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:443)
#15     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1392)
#16     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1313)
#17     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1171)
#18     _invoke (dart:ui/hooks.dart:312)
#19     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:419)
#20     _drawFrame (dart:ui/hooks.dart:283)