Forward port rev 1136822:

If presentwindows does not get activated, we have to revert the tabbox state or next activation is not possible.
CCBUG: 240730

svn path=/trunk/KDE/kdebase/workspace/; revision=1136823

effects/presentwindows/presentwindows.cpp

@@ -679,6 +679,8 @@ void PresentWindowsEffect::tabBoxAdded( int mode )
         setActive( true );
         if( m_activated )
             effects->refTabBox();
+        else
+            m_tabBoxEnabled = false;
         }
     }