Custom Post Type Archives (menu disppear)

I’am using Custom Post Type Archive and it causes my wp_nav to disappear. I found this WP Nav Menu Dissapears in Category Pages but didn’t seem to work. And I used is to add custom post to query

add_filter('pre_get_posts', 'query_post_type');
function query_post_type($query) {
  if(is_category() || is_tag()) {
    $post_type = get_query_var('post_type');
	if($post_type)
	    $post_type = $post_type;
	else
	    $post_type = array('post','press','nav_menu_item');
    $query->set('post_type',$post_type);
	return $query;
    }

I am pretty frustrated here. Please help! Thanks