tdf#116680 fix sidebar can't undock

Change-Id: Ic3d198488de6d0420dbdb8fb7dbfb0335556e108
Reviewed-on: https://gerrit.libreoffice.org/52047Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
Tested-by: Jenkins <ci@libreoffice.org>

sfx2/source/sidebar/SidebarDockingWindow.cxx

@@ -116,7 +116,7 @@ bool SidebarDockingWindow::EventNotify(NotifyEvent& rEvent)
     if (MouseNotifyEvent::KEYINPUT == nType)
         return true;
 
-    return Window::EventNotify(rEvent);
+    return SfxDockingWindow::EventNotify(rEvent);
 }
 
 } } // end of namespace sfx2::sidebar