commit c32e1e0ae0de97c963f8704cc846ecfb1292ccf6
Author: Joel Pittet <joel@pittet.ca>
Date:   Tue Jan 7 16:12:54 2014 -0800

    add default for pager

diff --git a/core/modules/forum/forum.module b/core/modules/forum/forum.module
index c214001..d87a4a4 100644
--- a/core/modules/forum/forum.module
+++ b/core/modules/forum/forum.module
@@ -624,6 +624,7 @@ function forum_theme_suggestions_forums(array $variables) {
  *   - forum_per_page: The maximum number of topics to display per page.
  */
 function template_preprocess_forums(&$variables) {
+  $variables['topics_pager'] = array();
   $variables['tid'] = $variables['term']->id();
   if ($variables['forums_defined'] = count($variables['forums']) || count($variables['parents'])) {
     if (!empty($variables['forums'])) {