Fixed crash when removing submenus in WPrefs' menu editor.

The submenu widget was free'd twice (once by destroyEditMenuItem() and a
second time by destroyEditMenu())

WPrefs.app/editmenu.c

@@ -1516,17 +1516,8 @@ handleItemClick(XEvent *event, void *data)
 static void
 destroyEditMenu(WEditMenu *mPtr)
 {
-    WEditMenuItem *item;
-    WMArrayIterator iter;
-
     WMRemoveNotificationObserver(mPtr);
 
-    WM_ITERATE_ARRAY(mPtr->items, item, iter) {
-        if (item->submenu) {
-            WMDestroyWidget(item->submenu);
-        }
-    }
-
     WMFreeArray(mPtr->items);
 
     wfree(mPtr->tdelegate);