Blender Git Loki

Fix T88394: crash when editing animated Alembic properties

When an object, whose mesh gets loaded from Alembic, gets animated in
Blender and the Alembic CacheFile datablock also gets animated, editing
keyframes causes both datablock to be re-copied for evaluation. This
caused a threading issue and a double-free of some memory. This is fixed
by expanding the scope of the spin lock in
`BKE_cachefile_reader_free()`.