changed if(isset($last) into if($last)

In line 75, $last gets set to false, hence it is set and an if-clause if(isset($last)) will always return true. Replaced it by if($last) which returns false as long as the setting by line 75 doesn't get changed by any value entered in the short code.

Topic was mentioned on http://wordpress.org/support/topic/error-in-shortcodesphp-line-96?replies=3