fix #8793 - NullPointerException in DistributeAction

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6006 0c6e7542-c601-0410-84e7-c038aed88b3b
fix #8794 - NumberFormatException in Geometry.getCentroid()

git-svn-id: http://josm.openstreetmap.de/svn/trunk@6007 0c6e7542-c601-0410-84e7-c038aed88b3b