the item is already children of us at this point, just make sure to not double add it.

i tried to find a way to reliably react to child add events instead of having to call our own method for this, but due to construction order and how itemChanged events are handled, i couldn't find such a thing. =/

svn path=/trunk/KDE/kdebase/workspace/libs/plasma/; revision=731137

widgets/widget.cpp

@@ -288,7 +288,7 @@ Widget *Widget::parent() const
 
 void Widget::addChild(Widget *w)
 {
-    if (!w || w->parent() == this) {
+    if (!w || d->childList.contains(w)) {
         return;
     }