JPEG files are detected as valid music files

[Bob]

When running with a folder that contain the album's cover as JPEG, SoundConverter will detect said JPEG files as valid audio files and add them to the conversion list.

Of course, this will later fail, and display an error message every single time a conversion is attempted (making it very tedious to use with the UI).

Cherry-picked lines from soundconverter --debug:

DEBUG: discoverer.py, line 138, found tag: cover-front.jpg
INFO: batch.py, line 346, skipping '/media/paul/9fb3c0d1-b778-47e2-8f1d-d26dc10bf4ea/Musique/The Best of Joe Cocker/The Best of Joe Cocker.m3u': not an audiofile
INFO: batch.py, line 346, skipping '/media/paul/9fb3c0d1-b778-47e2-8f1d-d26dc10bf4ea/Musique/The Best of Joe Cocker/The Best of Joe Cocker.cue': not an audiofile
INFO: batch.py, line 363, starting conversion of 19 files…
ERROR: error.py, line 30, gst-stream-error-quark: Internal data stream error. (1): /media/paul/9fb3c0d1-b778-47e2-8f1d-d26dc10bf4ea/Musique/The Best of Joe Cocker/cover-front.jpg

You can see that the .m3u and .cue files are correctly detected as not audio, but the JPEG file is detected as audio for whatever reason.

[sezanzeb (sezanzeb)]

Can reproduce, fix: https://github.com/kassoulet/soundconverter/pull/57