Messagebox error on comments

An error message appear when comments are created.
To fix it, i change fonction in line 43 of template.php file

function phptemplate_comment_wrapper($content, $type = null) {
  static $node_type;
  if (isset($type)) $node_type = $type;

  if (!$content || $node_type == 'forum') {
    return '<div id="comments">'. $content . '</div>';
  }
  else {
    return '<div id="comments"><h2 class="comments">'. t('Comments') .'</h2>'. $content .'</div>';
  }
}