WordPress: List Menu items, does NOT work with WP Nav Plus

file.php

        <?php $locations = get_nav_menu_locations(); ?>
        <?php $menu = wp_get_nav_menu_object( $locations['theme_location'] ); ?>
        <?php $menu_items = wp_get_nav_menu_items( $menu->term_id ); ?>

        <ul class="list-group list-group-flush">

        <?php foreach ( (array) $menu_items as $key => $menu_item ): ?>
          <li class="list-group-item list-group-item-action">
            <a href="<?= $menu_item->url; ?>">
              <?= $menu_item->title; ?>
            </a>
          </li>
        <?php endforeach; ?>
      </ul>