function lightbox_with_mixed_content_type() { 
?>
<script type="text/javascript">
window.addEventListener("DOMContentLoaded", function () { 
	(function($){
		$('.av-masonry.mixed-contenttype .av-masonry-entry').each(function(){
			if( $(this).filter('[data-av-masonry-custom-link]').length!==0 ){
				$(this).attr('rel', 'lightbox').addClass('mfp-iframe');
			}
		});	
	})(jQuery);
});
</script>
<?php 
}
add_action('wp_footer', 'lightbox_with_mixed_content_type', 999);