Allow Default Optgroups in "Main Frame Music"

[Enthalpy]

Currently, when selecting music for the main frame, you can only select music you’ve already used. The optgroups for default music are not available, unlike for regular frames. This is a fairly low priority, but should be an easy one to fix.

[Enthalpy]

To fix:

editor_frames_scene.js::606
music_descriptor -> music_select

Before pushing, check development history to see if there is a reason for this.

[ThePaSch]

This was fixed with the fade PR, which added a music editor to the Investigation block’s main frame options. The music editor does allow access to the default music optgroups. This can be closed.