Index: /trunk/src/org/openstreetmap/josm/data/osm/visitor/paint/relations/MultipolygonCache.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/data/osm/visitor/paint/relations/MultipolygonCache.java	(revision 13999)
+++ /trunk/src/org/openstreetmap/josm/data/osm/visitor/paint/relations/MultipolygonCache.java	(revision 14000)
@@ -81,5 +81,5 @@
     public Multipolygon get(Relation r, boolean forceRefresh) {
         Multipolygon multipolygon = null;
-        if (r != null) {
+        if (r != null && r.getDataSet() != null) {
             Map<Relation, Multipolygon> map2 = cache.get(r.getDataSet());
             if (map2 == null) {