Index: src/org/openstreetmap/josm/actions/JoinNodeWayAction.java
===================================================================
--- src/org/openstreetmap/josm/actions/JoinNodeWayAction.java	(revision 2420)
+++ src/org/openstreetmap/josm/actions/JoinNodeWayAction.java	(working copy)
@@ -59,9 +59,12 @@
 
         Collection<Command> cmds = new LinkedList<Command>();
         for (Map.Entry<Way, List<Integer>> insertPoint : insertPoints.entrySet()) {
+            List<Integer> is = insertPoint.getValue();
+            if (is.size() == 0)
+                continue;
+
             Way w = insertPoint.getKey();
             List<Node> nodesToAdd = w.getNodes();
-            List<Integer> is = insertPoint.getValue();
             pruneSuccsAndReverse(is);
             for (int i : is) {
                 nodesToAdd.add(i+1, node);
@@ -71,6 +74,9 @@
             cmds.add(new ChangeCommand(w, wnew));
         }
 
+        if (cmds.size() == 0)
+            return;
+
         Main.main.undoRedo.add(new SequenceCommand(tr("Join Node and Line"), cmds));
         Main.map.repaint();
     }