Blender Git Loki

Fix (unreported) potential issue in new `BKE_libblock_relink_to_newid_new`

Remapping code could call collection resync code while processing
remapping, which is a good way to crash by accessing no-more-valid
pointers.

Similar issue as with liboverrides resync, fixed the same way by
preventing any collection resync until whole remapping has been done.

This was probably not an issue in practice in current code, since this
is only used by append code currently, which should not affect
layers/collections in current scene yet.