Index: /trunk/src/org/openstreetmap/josm/gui/dialogs/ToggleDialog.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/gui/dialogs/ToggleDialog.java	(revision 3420)
+++ /trunk/src/org/openstreetmap/josm/gui/dialogs/ToggleDialog.java	(revision 3421)
@@ -462,5 +462,7 @@
 
         protected void rememberGeometry() {
-            Main.pref.put(preferencePrefix+".bounds", detachedDialog.getX()+","+detachedDialog.getY()+","+detachedDialog.getWidth()+","+detachedDialog.getHeight());
+            if (detachedDialog != null) {
+                Main.pref.put(preferencePrefix+".bounds", detachedDialog.getX()+","+detachedDialog.getY()+","+detachedDialog.getWidth()+","+detachedDialog.getHeight());
+            }
         }
     }