Axe-core parse error

[fniessink]

Describe the bug
Quality-time fails to parse this Axe-core JSON output:

[
    {
        "testEngine": {
            "name": "axe-core", 
            "version": "4.10.2"
        },
        "testEnvironment": {
            "userAgent": "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) HeadlessChrome/130.0.6723.31 Safari/537.36",
            "windowWidth": 1280,
            "windowHeight": 720,
            "orientationAngle": 0.0,
            "orientationType": "landscape-primary"
        },
       "timestamp": "2024-12-09T12:16:17.441Z",
       "url": "https://example.org"
   }
]

Traceback:

Traceback (most recent call last):
  File "/home/collector/base_collectors/source_collector.py", line 146, in __safely_parse_source_responses
    return await self._parse_source_responses(responses)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/collector/base_collectors/source_collector.py", line 159, in _parse_source_responses
    included_entities = [entity for entity in await self._parse_entities(responses) if self._include_entity(entity)]
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/collector/base_collectors/file_source_collector.py", line 113, in _parse_entities
    entities.extend(self._parse_json(json, filename))
                    ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^
  File "/home/collector/source_collectors/axe_core/violations.py", line 64, in _parse_json
    entity_attributes.extend(self.__parse_violations(violations, url))
                             ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/collector/source_collectors/axe_core/violations.py", line 82, in __parse_violations
    for violation in violations_by_result_type:
                     ^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: 'NoneType' object is not iterable

Your environment (please complete the following information):

• Quality-time v5.20.0