Have XMLTester use POINT EMPTY for a null return from getInteriorPoint

git-svn-id: http://svn.osgeo.org/geos/trunk@3747 5242fede-7e19-0410-aef8-94bd7d2200fb
Fix EMPTY return from zero-area polygon (#613)

git-svn-id: http://svn.osgeo.org/geos/trunk@3748 5242fede-7e19-0410-aef8-94bd7d2200fb