Notice: Undefined offset: 3 in _token_filter_filter_tokens

I enabled Page Manager and created a simple variant to display Node Content in a single Panels (7.x-3.0) column for Article types. It seems to work, but I get this notice at the top of each displayed article:

Notice: Undefined offset: 3 in _token_filter_filter_tokens() (line 36 of /home/user/website.com/sites/all/modules/token_filter/token_filter.module).

Here is the function in question:

function _token_filter_filter_tokens($text, $filter, $format, $langcode, $cache, $cache_id) {
  $data = array();
  $options = array();

  // Attempt to fetch the entity that is being viewed via a backtrace to the
  // field_attach_view($entity_type, $entity) function and parameters §if found.
  $backtrace = debug_backtrace();
  foreach ($backtrace as $caller) {
    if ($caller['function'] == 'field_attach_view') {
      $entity_type = $caller['args'][0];
      $entity = $caller['args'][1];
      $token_type = token_get_entity_mapping('entity', $entity_type);
      $data[$token_type] = $entity;
      // Use the proper language code that field_attach_view was called with.
      if ($langcode = $caller['args'][3]) {                                                  <-  THIS IS LINE 36
        $language_list = language_list();
        if (!empty($language_list[$langcode])) {
          $options['language'] = $language_list[$langcode];
        }
      }
      break;
    }
    elseif ($caller['function'] == '_drupal_bootstrap_full' || $caller == 'menu_execute_active_handler') {
      // There is no point in going back this far, so just stop.
      break;
    }
  }

  return token_replace($text, $data, $options);
}

the token_filter module is version 7.x-1.1

Any help?