Error when importing M4B with gapless set to true.

[SenorSmartyPants]

importing an M4B file with gapless attribute(pgap) set to true, mediafile generates an error. I encountered this error while testing Neurrone/beets-audible#15 but the stack trace does not touch on plugin. Perhaps this is related to the older version of mediafile installed? Latest version is 0.9.0

---

Expected Behavior

No error should occur if attribute is present.

Current Behavior

beet import -It .
Traceback (most recent call last):
  File "/usr/bin/beet", line 33, in <module>
    sys.exit(load_entry_point('beets==1.6.1', 'console_scripts', 'beet')())
  File "/usr/lib/python3.9/site-packages/beets/ui/__init__.py", line 1304, in main
    _raw_main(args)
  File "/usr/lib/python3.9/site-packages/beets/ui/__init__.py", line 1291, in _raw_main
    subcommand.func(lib, suboptions, subargs)
  File "/usr/lib/python3.9/site-packages/beets/ui/commands.py", line 973, in import_func
    import_files(lib, paths, query)
  File "/usr/lib/python3.9/site-packages/beets/ui/commands.py", line 943, in import_files
    session.run()
  File "/usr/lib/python3.9/site-packages/beets/importer.py", line 340, in run
    pl.run_parallel(QUEUE_SIZE)
  File "/usr/lib/python3.9/site-packages/beets/util/pipeline.py", line 446, in run_parallel
    raise exc_info[1].with_traceback(exc_info[2])
  File "/usr/lib/python3.9/site-packages/beets/util/pipeline.py", line 260, in run
    msg = next(self.coro)
  File "/usr/lib/python3.9/site-packages/beets/importer.py", line 1320, in read_tasks
    yield from task_factory.tasks()
  File "/usr/lib/python3.9/site-packages/beets/importer.py", line 1145, in tasks
    tasks = self._create(self.album(paths, dirs))
  File "/usr/lib/python3.9/site-packages/beets/importer.py", line 1224, in album
    items = [item for item in items if item]
  File "/usr/lib/python3.9/site-packages/beets/importer.py", line 1224, in <listcomp>
    items = [item for item in items if item]
  File "/usr/lib/python3.9/site-packages/beets/importer.py", line 1273, in read_item
    return library.Item.from_path(path)
  File "/usr/lib/python3.9/site-packages/beets/library.py", line 606, in from_path
    i.read(path)
  File "/usr/lib/python3.9/site-packages/beets/library.py", line 718, in read
    value = getattr(mediafile, key)
  File "/config/.local/lib/python3.9/site-packages/mediafile-0.6.0-py3.9.egg/mediafile.py", line 1198, in __get__
    out = style.get(mediafile.mgfile)
  File "/config/.local/lib/python3.9/site-packages/mediafile-0.6.0-py3.9.egg/mediafile.py", line 487, in get
    return self.deserialize(self.fetch(mutagen_file))
  File "/config/.local/lib/python3.9/site-packages/mediafile-0.6.0-py3.9.egg/mediafile.py", line 494, in fetch
    return mutagen_file[self.key][0]
TypeError: 'bool' object is not subscriptable

Steps to Reproduce

1. beet import -It gapless-set.m4b

Environment

OS:
CPU architecture: arm64
How docker service was installed:

armbian-config

Command used to create docker container (run/create/compose/screenshot)

  beets:
    image: lscr.io/linuxserver/beets:nightly
    container_name: beets
    environment:
      - TZ=${TZ}
      - PUID=${PUID}
      - PGID=100
    volumes:
      - /mnt/seagate4TB/appdata/beets:/config
      - /mnt/storage:/storage
    ports:
      - 8337:8337
    restart: unless-stopped

Docker logs

[SenorSmartyPants]

I just tried pip install --upgrade mediafile to 0.9.0 and that did not resolve the error.

[SenorSmartyPants]

Nevermind, cause of this error is not LSIO related.