In rB9c010c44f420, DRW_mesh_batch_cache_create_requested was changed to
take a scene (instead of toolsettings directly), but
DRW_draw_depth_object is calling this with with NULL, just checking for
this seems to fix...
Reviewers: fclem
Maniphest Tasks: T68675
Differential Revision: https://developer.blender.org/D5488