Critical when closing the prefs dialog
libxfce4panel-CRITICAL **: 10:29:01.356: IA__xfce_panel_plugin_unblock_menu: assertion 'plugin->priv->menu_blocked > 0' failed
libxfce4panel-CRITICAL **: 10:29:01.356: IA__xfce_panel_plugin_unblock_menu: assertion 'plugin->priv->menu_blocked > 0' failed