AppIndicator icons missing in GNOME

[grawity]

Steps to reproduce

I ran QuodLibet in GNOME with the "AppIndicator" GNOME Shell extension installed.

Expected Output

GNOME Shell's AppIndicator extension should show a "𝅘𝅥𝅮" QuodLibet icon.

Actual Output

GNOME Shell's AppIndicator extension shows a generic "⋯" icon and complains in the system log about:

Feb 28 10:15:15 frost [email protected][1765]: io.github.quodlibet.QuodLibet-1, Impossible
  to lookup icon for 'io.github.quodlibet.QuodLibet-symbolic' in /usr/lib/python3.11/site-packages/quodlibet/images

Test System

Which version of Quod Libet?

4.6.0

Which operating system

Arch Linux

If it's audio-related, what back-end?

It's not audio-related.

Additional Information

I had to manually create an index.theme file under /usr/lib/python3.11/site-packages/quodlibet/images/hicolor (then run gtk-update-icon-cache) to fix the issue locally: index.theme.txt