When assigning an Action with the new API:
- check the Actions ID type (if it is a legacy Action), and
- check whether the ID is in NLA tweak mode.
This means that action assignment can fail, so the
`animrig::assign_action()` and `animrig::unassign_action()` functions
now return a `[[nodiscard]] bool`.
Part of `generic_assign_action()` has now also been shielded with an
`#ifdef WITH_ANIM_BAKLAVA` just to be sure.
This also includes a change in `BKE_animdata_free()`. That function now
first exits NLA tweak mode (if enabled) before freeing the Actions. This
makes it possible to simply un-assign the assigned Action, as all the
NLA tweakmode stuff has already been taken care of by the responsible
function.
Pull Request: https://projects.blender.org/blender/blender/pulls/128199
fff6e59dde