smartGWT MenuBar - this.menus is undefined error

When you are attempting to add a smartGWT MenuBar to your screen, usually at system startup. If you get an error like this:

  com.google.gwt.core.client.JavaScriptException: (TypeError): this.menus is undefined

then check that you have used setMenus in when you first instantiate the menu bar. For example:
            MenuBar menuBar = new MenuBar();
           
            menuBar.setMenus(myFirstMenu,mySecondMenu);
           
            menuBar.setVisible(true);
            menuBar.setKeepInParentRect(false);

            RootPanel.get("menuPanel").add(menuBar);       


It is possible to use the add functions to add members and menus, but the underlying JavaScript needs a setMenu call to have the array that stores the menus initialised.