A simple workaround is to include this script section in your pages, after including hmenu.js:

<script type="text/javascript">
    DynarchMenu.__orig_setup = DynarchMenu.setup;
    DynarchMenu.setup = function(id, args) {
        var el = document.getElementById(id);
        if (el) {
            return DynarchMenu.__orig_setup(el, args);
        }
    };
</script>