Prevent a Gtk-CRITICAL message when Remove()ing a menu from a menubar

that has submenus.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@20319 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/menu.cpp

@@ -1124,7 +1124,8 @@ wxMenu::~wxMenu()
 {
    m_items.Clear();
 
-   gtk_widget_destroy( m_menu );
+   if ( GTK_IS_WIDGET( m_menu ))
+       gtk_widget_destroy( m_menu );
 
    gtk_object_unref( GTK_OBJECT(m_factory) );
 }