Blender Git Loki

Fix: Added some more tags/relations in depsgraph to fix crashes when Onion Skinning is enabled

* id_tag_update_object_data() - Added a case for the GP datablock type
so that depsgraph tagging via the GPencil datablock's RNA properties
works. Previously, only the object.data case (i.e. modifiers) was handled.
This fixes a crash when enabling onion skinning, and a ghost can be shown
on the neighbouring frames.

* DepsgraphRelationBuilder::build_obdata_geom() - Added a relation between
timesource and GP geometry (i.e. where cache rebuild occurs). This fixes
a crash after scrubbing the timeline when onion skinning is enabled
(I'm guessing due to onion skinning suddenly getting re-shown, but the cache
not doesn't contain this info due to the previously being updated for animation)