Refuse to set the RNA property `AnimData.animation_binding_handle` when
`AnimData.animation` is nil.
When in a hypothetical future `AnimData.animation` would be set, the
binding handle would be ignored anyway, as it's only meaningful within
the context of a known animation. Refusing to set the binding handle in
cases where it is known to be meaningless may help to find bugs in
Python scripts.
Pull Request: https://projects.blender.org/blender/blender/pulls/121268
c41f1be5b7