e80ceb52df
The issue was that the `AnimData.tmp_slot_handle` had no RNA property associated with it and so it couldn't be saved in the lib override. The fix is to add the property. To ensure the correct code is called, most of the previous code was replaced with a call to `blender::animrig::assign_tmpaction` Pull Request: https://projects.blender.org/blender/blender/pulls/141395