MangaDex sometimes returns None for translatedLanguages

[stranger-danger-zamu]

Expected behavior

Download all the chapters without issues.

Actual Behavior

Fails to handle calling str.partition on None and exits instantly.

Steps to Reproduce

1. Run the following command:

gallery-dl --verbose \
--chapter-filter 'lang == "en" and chapter >= 270' \
    https://mangadex.org/title/a96676e5-8ae2-425e-b549-7f15dd34a6d8/komi-san-wa-komyushou-desu

Context Information

OS: Linux (5.16.10)
Python: 3.10.2
gallery-dl version: 1.20.5

Debugging Log

#gallery-dl --verbose --chapter-filter 'lang == "en" and chapter >= 270' https://mangadex.org/title/a96676e5-8ae2-425e-b549-7f15dd34a6d8/komi-san-wa-komyushou-desu
[gallery-dl][debug] Version 1.20.5
[gallery-dl][debug] Python 3.10.2 - Linux-5.16.10-200.fc35.x86_64-x86_64-with-glibc2.34
[gallery-dl][debug] requests 2.27.1 - urllib3 1.26.8
[gallery-dl][debug] Starting DownloadJob for 'https://mangadex.org/title/a96676e5-8ae2-425e-b549-7f15dd34a6d8/komi-san-wa-komyushou-desu'
[mangadex][debug] Using MangadexMangaExtractor for 'https://mangadex.org/title/a96676e5-8ae2-425e-b549-7f15dd34a6d8/komi-san-wa-komyushou-desu'
[urllib3.connectionpool][debug] Starting new HTTPS connection (1): api.mangadex.org:443
[urllib3.connectionpool][debug] https://api.mangadex.org:443 "GET /manga/a96676e5-8ae2-425e-b549-7f15dd34a6d8/feed?order%5Bvolume%5D=asc&order%5Bchapter%5D=asc&contentRating%5B%5D=safe&contentRating%5B%5D=suggestive&contentRating%5B%5D=erotica&contentRating%5B%5D=pornographic&includes%5B%5D=scanlation_group&offset=0 HTTP/1.1" 200 None
[urllib3.connectionpool][debug] https://api.mangadex.org:443 "GET /manga/a96676e5-8ae2-425e-b549-7f15dd34a6d8?includes%5B%5D=artist&includes%5B%5D=author HTTP/1.1" 200 2450
[mangadex][error] An unexpected error occurred: AttributeError - 'NoneType' object has no attribute 'partition'. Please run gallery-dl again with the --verbose flag, copy its output and report this issue on https://github.com/mikf/gallery-dl/issues .
[mangadex][debug]
Traceback (most recent call last):
  File "/home/user/.local/pipx/venvs/gallery-dl/lib64/python3.10/site-packages/gallery_dl/job.py", line 76, in run
    for msg in extractor:
  File "/home/user/.local/pipx/venvs/gallery-dl/lib64/python3.10/site-packages/gallery_dl/extractor/mangadex.py", line 41, in items
    data = self._transform(chapter)
  File "/home/user/.local/pipx/venvs/gallery-dl/lib64/python3.10/site-packages/gallery_dl/extractor/mangadex.py", line 56, in _transform
    lang = cattributes["translatedLanguage"].partition("-")[0]
AttributeError: 'NoneType' object has no attribute 'partition'

Additional Information

#line 56 in gallery_dl/extractor/mangadex.py
lang = cattributes["translatedLanguage"].partition("-")[0]

to

_lang = cattributes.get('translatedLanguage') or ''
lang = _lang.partition('-')[0]

[mikf]

Filtering by language using mangadex's lang option would have also prevented this crash.