Index: trunk/src/org/openstreetmap/josm/gui/preferences/advanced/MapListEditor.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/advanced/MapListEditor.java	(revision 18223)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/advanced/MapListEditor.java	(revision 18224)
@@ -94,4 +94,5 @@
             dataKeys.add(new ArrayList<String>());
             dataValues.add(new ArrayList<String>());
+            dataLabels.add("");
             fireIntervalAdded(this, getSize() - 1, getSize() - 1);
         }
@@ -101,4 +102,5 @@
             dataKeys.remove(idx);
             dataValues.remove(idx);
+            dataLabels.remove(idx);
             fireIntervalRemoved(this, idx, idx);
         }