Blender Git Loki

bugfix [#25712] Deletion of vertex groups under script control causes incorrect reassignment of vertices in other groups

vgroup functions were mixing up active group and one passed as an argument.

also made other changes.
- removed superfluous call to defvert_find_index() in vgroup_delete_object_mode(), was also doing unnecessary NULL check on each loop.
- remove paranoid NULL check from ED_vgroup_vert_remove, callers all check for valid 'ob'