Index: /applications/editors/josm/plugins/reltoolbox/src/relcontext/ChosenRelation.java
===================================================================
--- /applications/editors/josm/plugins/reltoolbox/src/relcontext/ChosenRelation.java	(revision 36212)
+++ /applications/editors/josm/plugins/reltoolbox/src/relcontext/ChosenRelation.java	(revision 36213)
@@ -41,5 +41,5 @@
  */
 public class ChosenRelation implements ActiveLayerChangeListener, MapViewPaintable, DataSetListener {
-    protected Relation chosenRelation = null;
+    protected Relation chosenRelation;
     private final Set<ChosenRelationListener> chosenRelationListeners = new HashSet<>();
 
@@ -162,5 +162,5 @@
             for (OsmPrimitive element : rel.getMemberPrimitives()) {
                 if (null != element.getType()) {
-                    switch(element.getType()) {
+                    switch (element.getType()) {
                     case NODE:
                         Node node = (Node) element;
@@ -212,5 +212,8 @@
     public void dataChanged(DataChangedEvent event) {
         if (chosenRelation != null) {
-            fireRelationChanged(chosenRelation);
+            if (chosenRelation.getDataSet() == null)
+                clear();
+            else
+                fireRelationChanged(chosenRelation);
         }
     }