*** modules/comment/comment.module	2013-05-03 15:57:52.000000000 +0300
--- modules/comment/comment.module.patched	2013-06-03 04:15:30.000000000 +0300
*************** function comment_get_thread($node, $mode
*** 869,870 ****
--- 869,874 ----
  function comment_prepare_thread(&$comments) {
+ 
+   // trying to resolve https://drupal.org/node/1266620 (@tafkey, Jun 3, 2013) 
+   if (empty($comments)) return;
+ 
    // A flag stating if we are still searching for first new comment on the thread.