When a keying set is enabled and the keying set option
"Active Keying Set" was chosen from the menu, it would
give an error.
That is because the active keyingset uses a special
ID string (`"__ACTIVE__"`)
that doesn't actually exist as a keying set.
To fix it, explicitly check against that string and return
the active if encountered.
Pull Request: https://projects.blender.org/blender/blender/pulls/116192
1ea97dde6d