submenu-check.php

<?php
function public_nav_has_subpages() {
    $view = get_view();
    $nav = new Omeka_Navigation;
    $nav->loadAsOption(Omeka_Navigation::PUBLIC_NAVIGATION_MAIN_OPTION_NAME);
    $nav->addPagesFromFilter(Omeka_Navigation::PUBLIC_NAVIGATION_MAIN_FILTER_NAME);
    $pages = get_view()->navigation()->menu($nav)->getPages();
    foreach($pages as $page) {
        if($page->hasPages()) {
            return true;
        }
    }
    return false;
}