[-] FO : Fix bug #PSCSX-748

Fix for http://forge.prestashop.com/browse/PSCSX-748

Once again allows the use of URL's like this: 
<script src="//use.typekit.net/cak5ihv.js"></script>
after a recent commit https://github.com/PrestaShop/PrestaShop/commit/50ae04e019469d6d2928e27e454c777106b53c07 caused such lines to be removed completely.