Index: trunk/src/org/openstreetmap/josm/gui/preferences/PluginPreference.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/preferences/PluginPreference.java	(revision 3584)
+++ trunk/src/org/openstreetmap/josm/gui/preferences/PluginPreference.java	(revision 3585)
@@ -502,5 +502,7 @@
                             list.getSelectedValue()
                     );
-                    model.setElementAt(s, list.getSelectedIndex());
+                    if (s != null) {
+                        model.setElementAt(s, list.getSelectedIndex());
+                    }
                 }
             }), GBC.eol().fill(GBC.HORIZONTAL));