Fix T75279: BLI_assert failed when deleting object in debug build
(only).
And all general cases of ID pointer idproperties that would use a
data-block not referenced anywhere else in the depsgraph.
This includes idproperties from:
* All ID types;
* Bones and pose bones;
* Sequences;
* Nodes and sockets.
Differential Revision: https://developer.blender.org/D7551
37e08e526c