Index: trunk/src/org/openstreetmap/josm/gui/dialogs/ToggleDialog.java
===================================================================
--- trunk/src/org/openstreetmap/josm/gui/dialogs/ToggleDialog.java	(revision 3086)
+++ trunk/src/org/openstreetmap/josm/gui/dialogs/ToggleDialog.java	(revision 3087)
@@ -142,4 +142,6 @@
         private ToggleDialogAction(ToggleDialog dialog, String name, String iconName, String tooltip, Shortcut shortcut, String prefname) {
             super(name, iconName, tooltip, shortcut, false);
+            if (dialog == null)
+                throw new IllegalArgumentException("The ToggleDialog supplied for " + name + " cannot be null.");
             this.dialog = dialog;
         }