Find the cause of sponsorblock_categories becoming empty

[tcely]

I have confirmed that my settings are present in the database table immediately after I save the source.

sqlite> .headers on
sqlite> .mode line
sqlite> SELECT name, "sponsorblock_categories" FROM sync_source WHERE "enable_sponsorblock" ;
                       name = Reporting from Ukraine
    sponsorblock_categories = sponsor,outro,selfpromo,interaction
sqlite> 

However, at some later point they have been set to a blank string.

After refreshing the source, the categories are empty.

These tasks show up in completed tasks:

• Index media from source "Reporting from Ukraine" once
• Checking all media for source "Reporting from Ukraine"
• Renaming all media for source "Reporting from Ukraine"

I have narrowed it down to calling save() on the Source instance.

>>> source.refresh_from_db()
>>> source.sponsorblock_categories.selected_choices
['sponsor', 'outro', 'selfpromo', 'interaction']
>>> source.save()
>>> source.sponsorblock_categories.selected_choices
['sponsor', 'outro', 'selfpromo', 'interaction']
>>> source.refresh_from_db()
>>> source.sponsorblock_categories.selected_choices
[]
>>> 

See also:

• Build CommaSepChoiceField from CharField #669
• Fix CommaSepChoiceField #657
• Use yt_dlp.get_postprocessors() #655
• Use yt-dlp configuration for SponsorBlock #645
• Issue with SponserBlock / What is blocked. #362

Closes #362

[tcely]

@meeb Please review #680, as I think it fixes the problem points.