No cover images are displayed for `m4b` audio files, if covers are file embedded

[sandreas]

Bug report

Describe the bug

No cover images are displayed for m4b audio files, if covers are file embedded, although cover is embedded in file. Maybe this is problem in Kodi itself, not storing or accessing the embedded covers correctly.

Expected Behavior

Embedded covers are displayed for all audio files (if there is not an extra image file)

Actual Behavior

Details:

• I use m4b-tool to create m4b files for my audio books
• These files are meant to be "all in one" (Metadata, Cover, Chapters) - so putting an extra cover.jpg in the directory is not intended
• Chorus2 does not display these covers (see Screenshot)

To Reproduce

Steps to reproduce the behavior:

1. Import the attached m4b into your library (see below)
2. Open Web-Interface
3. Image is not shown, although e.g. VLC Media Player shows the embedded cover

Debuglog

!No debug Log output!

Screenshots

Additional context or screenshots (if appropriate)

Sample m4b: out.m4b.zip

Your Environment

Used Operating system:

• Used browser(s): Firefox 94
• Operating system version/name: Ubuntu 18.04 LTS
• Kodi version and platform: 19.x-2.4.8
• Chorus2 version:19.3