Handle case when the target EditPart in PartUtil's X/Y coordinate
calculation may be null (i.e., after auto-layout has been done + addtl.
nodes have been added for which EPs aren't present in the EPRegistry yet
as they will be after current EP in the list of parten's children).
Add check on whether SDomRels and SSpanRels may be executed
Move check on whether relation create command ca nwork to policy