<nav id="main-nav"<?php echo $stick; ?>>
<?php $orig_post = $post; wp_nav_menu( array( 'container_class' => 'main-menu', 'theme_location' => 'primary-nav' ,'fallback_cb' => 'tie_nav_fallback',  'walker' => new tie_mega_menu_walker()  ) ); $post = $orig_post; ?>
</nav>