Index: applications/editors/josm/plugins/navigator/src/at/dallermassl/josm/plugin/navigator/OsmGraphCreator.java
===================================================================
--- applications/editors/josm/plugins/navigator/src/at/dallermassl/josm/plugin/navigator/OsmGraphCreator.java	(revision 3891)
+++ applications/editors/josm/plugins/navigator/src/at/dallermassl/josm/plugin/navigator/OsmGraphCreator.java	(revision 3892)
@@ -58,7 +58,7 @@
         // iterate all ways and segments for all nodes:
         for(Way way : Main.ds.ways) {
-            if(!way.deleted) {                
+            if(way != null && !way.deleted) {                
                 for(Segment segment : way.segments) {
-                    if(!segment.deleted) {
+                    if(segment != null && !segment.deleted && segment.from != null && segment.to != null) {
                         graph.addVertex(segment.from);
                         graph.addVertex(segment.to);