Index: /trunk/src/org/openstreetmap/josm/gui/conflict/pair/properties/PropertiesMergeModel.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/conflict/pair/properties/PropertiesMergeModel.java	(revision 3060)
+++ /trunk/src/org/openstreetmap/josm/gui/conflict/pair/properties/PropertiesMergeModel.java	(revision 3061)
@@ -9,4 +9,5 @@
 import java.beans.PropertyChangeSupport;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -179,6 +180,6 @@
         theirVisibleState = their.isVisible();
 
-        myReferrers = my.getReferrers();
-        theirReferrers = their.getReferrers();
+        myReferrers = my.getDataSet() == null?Collections.<OsmPrimitive>emptyList():my.getReferrers();
+        theirReferrers = their.getDataSet() == null?Collections.<OsmPrimitive>emptyList():their.getReferrers();
 
         coordMergeDecision = UNDECIDED;