continuous SoundSourceProvider error messages when files are missing

[RJ Skerry-Ryan]

Repro steps:

1) New library
2) Add a folder of music
3) Move that folder somewhere else
4) Restart Mixxx

Scrolling through the library shows constant errors messages:

Warning [Thread (pooled)]: Unsupported file type: "file:"
Warning [Thread (pooled)]: No SoundSourceProvider for file "file:"
Warning [Thread (pooled)]: Unsupported file type: "file:"
Warning [Thread (pooled)]: No SoundSourceProvider for file "file:"
Warning [Thread (pooled)]: Unsupported file type: "file:"
Warning [Thread (pooled)]: No SoundSourceProvider for file "file:"
Warning [Thread (pooled)]: Unsupported file type: "file:"
Warning [Thread (pooled)]: No SoundSourceProvider for file "file:"
Warning [Thread (pooled)]: Unsupported file type: "file:"
Warning [Thread (pooled)]: No SoundSourceProvider for file "file:"
Warning [Thread (pooled)]: Unsupported file type: "file:"
Warning [Thread (pooled)]: No SoundSourceProvider for file "file:"

1) Why are we constantly trying to touch the filesystem on scrolling in the Library (not browse mode). Trying to read cover art? That seems non-ideal.
2) SoundSourceProvider's URL seems to be lost ("file:") when the file doesn't exist. Is that because we take the absolute/canonical path?
3) Let's not print for this particular error case :).

[Uwe Klotz (uklotzde-deactivatedaccount)]

Yes and yes:
1) It's that cover art that gets reloaded constantly
2) The canonical/absolute file path of a non-existent file is empty

[Uwe Klotz (uklotzde-deactivatedaccount)]

https://github.com/mixxxdj/mixxx/pull/946

[Swiftb0y (swiftb0y)]

Mixxx now uses GitHub for bug tracking. This bug has been migrated to:
https://github.com/mixxxdj/mixxx/issues/8545