Use GTK_OBJECT_GET_CLASS macro.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@7785 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk1/control.cpp

@@ -73,7 +73,7 @@ wxSize wxControl::DoGetBestSize() const
     GtkRequisition req;
     req.width = 2;
     req.height = 2;
-    (* GTK_WIDGET_CLASS( GTK_OBJECT(m_widget)->klass )->size_request )
+    (* GTK_WIDGET_CLASS( GTK_OBJECT_GET_CLASS(m_widget) )->size_request )
         (m_widget, &req );
 
     return wxSize(req.width, req.height);