$icon variable undefined in line 21 of forum-icon.tpl.php

Possibly the name of the variable has changed? It appears that the correct name should now be $icon_class. Below, I have changed the two occurances of $icon to $icon_class in forum-icon.tpl.php and it appears to work just fine. The error had showed up when listing a forum which contained any content.

// $Id: forum-icon.tpl.php,v 1.4 2010/06/18 14:02:28 jarek Exp $

/**
 * @file
 * Default theme implementation to display an appropriate icon for a forum post.
 *
 * Available variables:
 * - $new_posts: Indicates whether or not the topic contains new posts.
 * - $icon_class: The icon to display. May be one of 'hot', 'hot-new', 'new',
 *   'default', 'closed', or 'sticky'.
 *
 * @see template_preprocess_forum_icon()
 * @see theme_forum_icon()
 */

if ($new_posts):

endif;

print theme('image', array('path' => $directory . "/images/forum-$icon_class.png", 'alt' => 'Default avatar'));

if ($new_posts):

endif;