Added additional check to avoid IndexError

Summary of the Pull Request

This PR aims to fix, that the check_type_mismatch(self, check_value) method of the ParamArray(ParamBase) class can cause a IndexError.

PR Checklist

[x] Applies to work item: engine/fuzzing_parameters/request_params.py
[x] CLA signed.
[ ] Tests added/passed
[ ] Requires documentation to be updated
[ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different approach. Issue number where discussion took place:

Info on Pull Request

While testing restlers fuzzing mode I ran into an IndexError caused by the previously mentioned method. To fix this, I added an additional check to test if self._values has a first element in case it is of type list. If not the self.tag is returend. I'm not quite sure if the tool should react this way if the self._values is a list but empty. Might be a sign of another bug if this scenario shouldn't happen at all. For me, it allowed the tool to run in fuzzing mode.

EngineStdOut.txt of the error run:

2024-06-10 15:31:02.567: Initializing: Garbage collection every 30 seconds.
2024-06-10 15:31:02.678: Generation: 1 
Invalid value generator random seed: 1718026263.7919257
Setting invalid value generator random seed: 12345
...
Invalid value generator random seed: 1718026555.0672019
Setting invalid value generator random seed: 12345
Exception list index out of range applying checker <checkers.payload_body_checker.PayloadBodyChecker object at 0x000001C83488DF10>
2024-06-10 15:36:19.457: Terminating garbage collection. Waiting for max 300 seconds. 
Traceback (most recent call last):
  File "C:\restler_bin\engine\engine\core\fuzzer.py", line 43, in run
    self._num_total_sequences = driver.generate_sequences(
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\engine\core\driver.py", line 835, in generate_sequences
    seq_collection = render(seq_collection, fuzzing_pool, checkers, generation, global_lock,
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\engine\core\driver.py", line 331, in render_sequential
    valid_renderings = render_one(seq_collection[ith], ith, checkers, generation, global_lock, garbage_collector)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\engine\core\driver.py", line 225, in render_one
    apply_checkers(checkers, renderings, global_lock)
  File "C:\restler_bin\engine\engine\core\driver.py", line 156, in apply_checkers
    checker.apply(renderings, global_lock)
  File "C:\restler_bin\engine\checkers\payload_body_checker.py", line 188, in apply
    self._run_feedback_fuzzing(last_request, body_schema_list)
  File "C:\restler_bin\engine\checkers\payload_body_checker.py", line 641, in _run_feedback_fuzzing
    self._run_invalid_json_task(
  File "C:\restler_bin\engine\checkers\payload_body_checker.py", line 743, in _run_invalid_json_task
    self._run_body_value_fuzzing(
  File "C:\restler_bin\engine\checkers\payload_body_checker.py", line 849, in _run_body_value_fuzzing
    self._exec_request_with_new_body(request, body_blocks, tracker)
  File "C:\restler_bin\engine\checkers\payload_body_checker.py", line 1239, in _exec_request_with_new_body
    bug_info = self._buckets.add_bug(request, rendered_data)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\checkers\payload_body_bucketing.py", line 39, in add_bug
    error_str = self._get_error_str(request, new_body) or 'Other'
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\checkers\payload_body_bucketing.py", line 64, in _get_error_str
    mismatch = request.body_schema.has_type_mismatch(new_body)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\engine\fuzzing_parameters\body_schema.py", line 263, in has_type_mismatch
    return self._schema.check_type_mismatch(new_body)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\engine\fuzzing_parameters\request_params.py", line 663, in check_type_mismatch
    tag = member.check_type_mismatch(check_value)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\engine\fuzzing_parameters\request_params.py", line 1725, in check_type_mismatch
    return self.value.check_type_mismatch(check_value[self.name])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\restler_bin\engine\engine\fuzzing_parameters\request_params.py", line 858, in check_type_mismatch
    return self._values[0].check_type_mismatch(new_check)
           ~~~~~~~~~~~~^^^
IndexError: list index out of range

Validation Steps Performed

Run the tool with the modified code in fuzzing mode without encountering the IndexError.

microsoft / restler-fuzzer