Fixed youtube subscription import: ignore ones with invalid url and keep ones with empty title.

[Stypox]

• I carefully read the contribution guidelines and agree to them.
• I did test the API against NewPipe.
• [no breaking change] I agree to ASAP create a PULL request for NewPipe for making in compatible when I changed the api.

Now when the YoutubeSubscriptionExtractor parses the YouTube subscription_manager file, it ignores channels that have no title, instead of throwing an error: that file can sometimes natively contain channels with no title (i.e. deleted channels).

I tested the changes inside the NewPipe app against the file provided in TeamNewPipe/NewPipe#2226. I also added a unit test.

I left untouched all the other "document has invalid entries" exceptions, since they are not involved in the empty-title issue. I think this is ok.

Fix TeamNewPipe/NewPipe#2226

[mauriciocolli]

Thanks for the pull request!

I think we should remove the check for the title, and leave only the url one (the essential part).

Like I commented in the issue, I think YouTube does this for channels deleted OR suspended. The channels that are suspended can come back (rarely), so what if the user export before it comes back and tries to import after it comes back? It just won't show up.

I say we should let this entry go and let the importing service handle it (which is simply ignoring the failing entry at this moment), what do you think?

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Edit: After thinking a little more about it, should we fail immediately after we don't find a invalid url? Or be more lenient about it (just ignore the entry)?

I'm leaned towards being more lenient.

[TobiGr]

After thinking a little more about it, should we fail immediately after we don't find a invalid url? Or be more lenient about it (just ignore the entry)?

Yes, we should ignore and not fail to import. Maybe return the number of imports/urls which caused a problem and then display a toast / dialog which or how many subscriptions could not be imported.

[Stypox]

I don't think it would be much useful for the user to know how many subscriptions couldn't be imported. And that number will be 0 most of the times (if not always: a subscription with an empty title still has a valid url). I would just do what mauriciocolli suggested: ignoring the extremely rare invalid entries.