tweak to recent commit to clamp vertex range so new empty vgroups are in fact empty.
- don't clamp if no empty groups are created
- no need to call ED_vgroup_data_create, this was very old code for weight paint r1596 - weight paint works without adding 'dvert'array.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@54012 954f8c5b-7b00-dc11-b283-0030488c597c