Fix wrong assumption that 'embedded' IDs are only ever used by their owners. This is especially not true with shape keys. Also small optimization by adding an eraly abort when both IDs are the same (i.e. an ID has a pointer to itself).
Fix wrong assumption that 'embedded' IDs are only ever used by their owners. This is especially not true with shape keys. Also small optimization by adding an eraly abort when both IDs are the same (i.e. an ID has a pointer to itself).