In r1.395, I forgot to unmap the wrapper window too. As it has no background

set, it remembers the contents of the unmapped client window, therefore
the ugly effect actually stayed.

svn path=/trunk/kdebase/kwin/; revision=273891

client.cpp

@@ -176,6 +176,7 @@ void Client::releaseWindow( bool on_shutdown )
         {
         workspace()->clientHidden( this );
         XUnmapWindow( qt_xdisplay(), window()); // destroying decoration would cause ugly visual effect
+        XUnmapWindow( qt_xdisplay(), wrapperId());
         }
     destroyDecoration();
     cleanGrouping();