Index: trunk/src/org/openstreetmap/josm/gui/mappaint/ElemStyles.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/mappaint/ElemStyles.java	(revision 5765)
+++ trunk/src/org/openstreetmap/josm/gui/mappaint/ElemStyles.java	(revision 5766)
@@ -112,5 +112,7 @@
             }
         }
-        osm.mappaintStyle = osm.mappaintStyle.put(p.a, p.b);
+        if (p != null) {
+            osm.mappaintStyle = osm.mappaintStyle.put(p.a, p.b);
+        }
         osm.mappaintCacheIdx = cacheIdx;
         return p;