correcion a blank menu (Foreach)

correcion a blank menu

$items = wp_get_nav_menu_items($slug);
    if (is_array($items)) {
     $menuhtml = '<ul class="menu">';
    $menui = 0;
    foreach ($items as $menuitem) {
	$class = '';
	$submenu = '';
	if ($menuitem->object_id == $post->ID) {
	    $class = "current";
	} else if ($menuitem->object_id == $post->post_parent) {
	    $class = "current";
	}
	if(0==$menui){
	    $class .= ' first';
	}
	if($menuitem->menu_item_parent){
	    $class .= ' submenu';
	}
	if(""!=$class){
	    $class = 'class="'.$class.'"';
	}
	$menuhtml .= '<li '.$class.'><a href="' . $menuitem->url . '">' . $menuitem->title . '</a></li>';
	if(''!=$submenu){
	    $menuhtml .= '<li>'.$submenu.'</li>';
	}
	$menui++;
    }
    $menuhtml .= '</ul>';
    }
    echo $menuhtml;
}

edit the file page_navmenu.php plugins folder
Note: run wordpress 3.7.1 ??
https://www.ads-software.com/plugins/page-navigation-menu/