addClass interfering with 'scroll-to-top' function

I'm using parts of a template with MDB and the 'scroll-to-top' chevron function to scroll to top of the page is not working. The first time I click nothing happens and nothing pops up in the console, but from the second click I get this error:

Uncaught DOMException: Failed to execute 'add' on 'DOMTokenList': The token provided must not be empty. at Object.addClass (http://127.0.0.1:8000/static/js/mdb.min.js:19:75896) at hr._addAnimatedClass (http://127.0.0.1:8000/static/js/mdb.min.js:19:179258) at hr._startAnimation (http://127.0.0.1:8000/static/js/mdb.min.js:19:179472) at HTMLHtmlElement. (http://127.0.0.1:8000/static/js/mdb.min.js:19:181109) at HTMLHtmlElement.t (http://127.0.0.1:8000/static/js/mdb.min.js:19:73407)

Refering to 'manipulator.js' on line 99. This is the function on manipulator.js:

addClass(element, className) { if (element.classList.contains(className)) return; element.classList.add(className); },

This is a part of the scroll-to-top function that triggers the error:

        build: function() {
            var self = this,
                $el;

            // Base HTML Markup
            $el = $('<a />')
                .addClass(self.options.buttonClass)
                .attr({
                    'href': '#header',
                })
                .append(
                    $('<i />')
                    .addClass(self.options.iconClass)
            );

buttonClass is just 'scroll-to-top'. What can it be the problem?