tdf#92088: Fix an overlook in the refactor.

This was causing 'if you click in the "default style" combobox in writers
standard bar and press tab and press tab the next two combo boxes go "blue",
happens in gtk2, gtk3 and gen.' reported by Caolan.

Change-Id: I0d97a181a605088a0b8bb8043771eb56280521e0

vcl/source/window/toolbox.cxx

@@ -5612,10 +5612,8 @@ void ToolBox::ImplShowFocus()
         ImplToolItem* pItem = ImplGetItem( mnHighItemId );
         if( pItem->mpWindow && !pItem->mpWindow->IsDisposed() )
         {
-            WindowImpl *pItemImpl = pItem->mpWindow->ImplGetWindowImpl();
-            vcl::Window *pWin = pItemImpl->mpBorderWindow ?
-                pItemImpl->mpBorderWindow : pItem->mpWindow;
-            pItemImpl->mbDrawSelectionBackground = true;
+            vcl::Window *pWin = pItem->mpWindow->ImplGetWindowImpl()->mpBorderWindow ? pItem->mpWindow->ImplGetWindowImpl()->mpBorderWindow : pItem->mpWindow;
+            pWin->ImplGetWindowImpl()->mbDrawSelectionBackground = true;
             pWin->Invalidate();
         }
     }