Use the new `action.fcurve_ensure_for_datablock()` function to ensure
the opacity F-Curve exists.
This function also ensures that the Action itself is ready for keying
(it has a layer and a keyframe strip), and ensures the slot for the
Scene exists and is assigned.
Co-authored-by: Pratik Borhade <pratikborhade302@gmail.com>
Pull Request: https://projects.blender.org/blender/blender/pulls/134753
0bb750ee84