SUMMARY
Cover art for tracks with no album meta data don't display their cover art.

STEPS TO REPRODUCE
1. Disable the baloo file indexer.
2. Put a track without album meta data in your Music folder.
3. Open Elisa and browse to the added track.

OBSERVED RESULT
The green cd placeholder is seen in place of the cover art, to the left of the track's name in the 'Tracks' menu.

EXPECTED RESULT
The cover art displays where expected, left of the track's name in the 'Tracks' menu.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSUSE Tumbleweed 20201009
(available in About System)
KDE Plasma Version: 5.19.5
KDE Frameworks Version: 5.74.0
Qt Version: 5.15.1

ADDITIONAL INFORMATION
The tracks that are affected are too large to be attached directly, so here's a link to one of them in my google drive:
https://drive.google.com/file/d/1tt4Mp_aibPCWnQ7kTznoKjhjLmVOO7uS/view?usp=sharing