adding items to nav-menu

Im using the 3.8 version of wordpress and I’m trying to add some custom social items to the navigation menu – something I’ve done several times before on previous versions of wp. But for some reason i simply can’t get it to work now.

Here is my code, put into the child themes functions.php:

<?php
/**
*functions.php for Child theme
*/

/* Social Icons */

function menu_social($items){
    $social = '<li class="social">';
    $social .= '<a href="https://www.facebook.com/christel.winther">';
	$social .= '<img src="https://selgolb.cphadsdemo.dk/wp-content/themes/christel/images/facebook.png" /> </a>';
	$social .= '<a href="https://twitter.com/ChristelWinther">';
	$social .= '<img src="https://selgolb.cphadsdemo.dk/wp-content/themes/christel/images/twitter.png" /> </a>';
	$social .= '<a href="dk.linkedin.com/pub/christel-winther/2/409/b03">';
	$social .= '<img src="https://selgolb.cphadsdemo.dk/wp-content/themes/christel/images/linkedin.png" /> </a>';
	$social .= '<a href="https://christelwinther.com/feed">';
	$social .= '<img src="https://selgolb.cphadsdemo.dk/wp-content/themes/christel/images/rss.png" /> </a>';
	$social .= '</li>';

    return $items . $social;
}
add_filter('wp_nav_menu_items','menu_social');

?>

The website url is: https://selgolb.cphadsdemo.dk