Started to happen after recent fix for T72632.
Was caused by runtime fields backup doing an early exit in the case the
given ID was never expanded by the Copy-on-Write mechanism, but it was
not done int the backup restore function (since it was not possible to
know "locally").
Now both init() and restore() will do an early exit when the ID had
nothing to be backed up.
The issue was caused by special handling of animation update after
manual edits in frame_post handler: to avid loss of manual edits
done on top of animated property. This was done as a separate pass
for non-animation update after frame_post did modifications.
This caused some other side-effect: non-modified animated property
was re-setting to the value which is used in the viewport.
Idea of this solution is simple: preserve values which came from
animation update through copy-on-write process. The actual process
of this is a bit involved: need to decode RNA path and do it twice
since f-curve might point to a sub-data which pointer will change.
Since this is only done for non-active depsgraph (aka depsgraph
used for render pipeline) this is probably fine since all this
extra overhead is just a fraction of overall render process.
Differential Revision: https://developer.blender.org/D6330
