Backport of "pbutils: descriptions: Don't warn on MPEG-1 audio caps without layer field" into 1.24
Backport of !6511 (merged) "pbutils: descriptions: Don't warn on MPEG-1 audio caps without layer field".
Commits:
- 4b5a2655 pbutils: descriptions: Don't warn on MPEG-1 audio caps without layer field