Order posts by meta value hiding posts instead of re-ordering

Question

The code below is suppose to display all posts with "featured_listing" meta key above all of the standard posts.

When the below code is in the functions.php, it hides all posts without "featured_listing" meta. Instead of showing them below the featured listings.

function custom_special_sort( $query ) {
     if ( is_admin() || ! $query->is_main_query() ) {
        return;
    }
    // if is this the main query and is this post type of business
    if ( (is_post_type_archive('business') ) || (is_tax ('location') ) ) {

        // order results by the meta_key 'featured_listing'
       $query->set( 'meta_key', 'featured_listing' );
        $query->set( 'orderby', 'featured_listing' );
        $query->set( 'order', 'DESC' );

    }
}
add_action( 'pre_get_posts', 'custom_special_sort' );

Answer 1

Literally seconds after updating this post I found the solution....again, Must have looked at this previously and not entered the details correctly as I tried this one before. :)

    add_action('pre_get_posts', 'add_special_sort', 11, 1);
function add_special_sort($query){
  // Bail if not the main "hidden" query, as opposed to a 'new WP_Query()' call
  if(!$query->is_main_query())
    return;

  $query->set('meta_query', array(
    'relation' => 'OR',
    array(
      'key' => 'featured_listing',
      'compare' => 'NOT EXISTS',
    ),
    array(
      'key' => 'featured_listing',
      'compare' => 'EXISTS',
    )
  ));
  //$query->set('meta_key', NULL);
  $query->set('orderby', array('meta_value_num' => 'DESC', 'date' => 'DESC'));
}