Array_merge Warning in Semantic fields settings

When i edit my view in Format > Show: (Semantic Views:Fields) Settings it first takes a very long time to come up (atleast 10 seconds), and i then i get this error:

Warning: array_merge(): Argument #1 is not an array in array_merge() (line 4194 of /home/dev/drupal-7.x/includes/form.inc). =>

otherwise everything seems to work.

for convenience, here is the relevant part from includes/form.inc >

/**
 * Sets a form element's class attribute.
 *
 * Adds 'required' and 'error' classes as needed.
 *
 * @param $element
 *   The form element.
 * @param $name
 *   Array of new class names to be added.
 */
function _form_set_class(&$element, $class = array()) {
  if (!empty($class)) {
    if (!isset($element['#attributes']['class'])) {
      $element['#attributes']['class'] = array();
    }
/**LINE 4194**/    $element['#attributes']['class'] = array_merge($element['#attributes']['class'], $class);
  }