case 'winfirst':
        $wp_query_args['meta_query'] = array(
                 'relation' => 'OR',
                 'query_one' => array(
                 'key' => 'wedstrijd',
                 'compare' => '=',
                 'value' => '1'
                                             ),
                 'query_two' => array(
                 'key' => 'wedstrijd',
                 'compare' => '=',
                 'value' => '',
    ),
);
$wp_query_args['orderby'] = array( 'query_one' => 'ASC', 'query_two' => 'DESC');