Uncaught type error: Cannot call method 'split' of undefined

I’m getting this error in Google Chrome dev tools. It shows up in this code:

var disqus_shortname = '<?php echo strtolower(get_option('disqus_forum_url')); ?>';
        (function () {
            var nodes = document.getElementsByTagName('span');
            for (var i = 0, url; i < nodes.length; i++) {
                if (nodes[i].className.indexOf('dsq-postid') != -1) {
                    nodes[i].parentNode.setAttribute('data-disqus-identifier', nodes[i].getAttribute('rel'));
                    url = nodes[i].parentNode.href.split('#', 1);
                    if (url.length == 1) { url = url[0]; }
                    else { url = url[1]; }
                    nodes[i].parentNode.href = url + '#disqus_thread';
                }
            }
            var s = document.createElement('script'); s.async = true;
            s.type = 'text/javascript';
            s.src = '//' + '<?php echo DISQUS_DOMAIN; ?>/forums/' + disqus_shortname + '/count.js';
            (document.getElementsByTagName('HEAD')[0] || document.getElementsByTagName('BODY')[0]).appendChild(s);
        }());

I tried using the option that puts Javascript in the footer since it seems like some people fixed their errors that way, but it still shows up.

https://www.ads-software.com/plugins/disqus-comment-system/