fix(ngAnimate): ensure that only string-based addClass/removeClass values are applied - #12459

function addRemoveClassesPostDigest(element, add, remove) {
  var data = postDigestQueue.get(element);
  var updated = false;
  var classVal;

  var updateData = function(classes, value) {
    var changed = false;
    if (classes) {
      classes = isString(classes) ? classes.split(' ') :
                isArray(classes) ? classes : [];
      forEach(classes, function(className) {
        if (className) {
          changed = true;
          data[className] = value;
        }
      });
    }
    return changed;
  };

  if (!data) {
    postDigestQueue.put(element, data = {});
    postDigestElements.push(element);
  }

  updated = updateData(add, true);
  updated = updated || updateData(remove, false);


  if (!updated || postDigestElements.length > 1) return;

  ...