anchor.diff:                  if ((bodyScrlPos >= tablTop - menuHeight - listHeight) && (bodyScrlPos < nextItem - menuHeight - listHeight)) {
                     list.childNodes[i].classList.add(activeClass);
                   } else {
  -                  list.childNodes[i].classList.remove(activeClass);
  +                  //condition to prevent Type Error
  +                  if (typeof list.childNodes[i] !== 'undefined') {
  +                    list.childNodes[i].classList.remove(activeClass);
  +                  }
                   }
                 });
               } else {
  
positive.code:               list.style.top = menuHeight + 'px';
                
                //make tabs "stick" to confBottom
                if (bodyScrlPos > ((confTopPos + confHeight) - listHeight - menuHeight)) {
                  list.style.top = confBottom - bodyScrlPos - listHeight + 'px';
                }
                
                //this chunk is for selecting proper tab due to scrollTop
  
negative.code:       var info = session.getElementsByClassName('session__info')[0];
        icon.classList.toggle('session__icon--expanded');
        about.classList.toggle('invisible');
        if (viewport <= #{config.breakPoint}) {
          info.classList.toggle('invisible');
        }
      }
      
      (function() {
  