Videos no longer play

[QTE113]

When videos try to play, they just appear as a black screen. I believe that popup.pyw is the problem, as line 226 tests if not isinstance(self.audio_track):, which throws an error since isinstance expects two arguments. Bringing back from types import NoneType and changing the test back to if not isinstance(self.audio_track, NoneType): seems to fix the issue.

[puppy-brain]

My guess is that the intention was to move away from the unnecessary isinstance check altogether and rely on Python's native truthy values for objects instead?

Have tested this fix and it looks like it works as well.

@PetitTournesol I would submit a Pull Request for this fix if you'd like but believe I'd need to be added to the project before doing so.