Caught AttributeError while rendering: class MpttMeta has no attribute '__class__'

posts = topic.posts.all().select_related()

SELECT `djangobb_forum_post`.`id`, 
       `djangobb_forum_post`.`topic_id`, 
       `djangobb_forum_post`.`user_id`, 
       `djangobb_forum_post`.`created`, 
       `djangobb_forum_post`.`updated`, 
       `djangobb_forum_post`.`updated_by_id`, 
       `djangobb_forum_post`.`markup`, 
       `djangobb_forum_post`.`body`, 
       `djangobb_forum_post`.`body_html`, 
       `djangobb_forum_post`.`user_ip`, 
       `djangobb_forum_topic`.`id`, 
       `djangobb_forum_topic`.`forum_id`, 
       `djangobb_forum_topic`.`name`, 
       `djangobb_forum_topic`.`created`, 
       `djangobb_forum_topic`.`updated`, 
       `djangobb_forum_topic`.`user_id`, 
       `djangobb_forum_topic`.`views`, 
       `djangobb_forum_topic`.`sticky`, 
       `djangobb_forum_topic`.`closed`, 
       `djangobb_forum_topic`.`post_count`, 
       `djangobb_forum_topic`.`last_post_id`, 
       `djangobb_forum_forum`.`id`, 
       `djangobb_forum_forum`.`category_id`, 
       `djangobb_forum_forum`.`name`, 
       `djangobb_forum_forum`.`position`, 
       `djangobb_forum_forum`.`description`, 
       `djangobb_forum_forum`.`updated`, 
       `djangobb_forum_forum`.`post_count`, 
       `djangobb_forum_forum`.`topic_count`, 
       `djangobb_forum_forum`.`last_post_id`, 
       `djangobb_forum_category`.`id`, 
       `djangobb_forum_category`.`name`, 
       `djangobb_forum_category`.`position`, 
       `auth_user`.`id`, 
       `auth_user`.`username`, 
       `auth_user`.`first_name`, 
       `auth_user`.`last_name`, 
       `auth_user`.`email`, 
       `auth_user`.`password`, 
       `auth_user`.`is_staff`, 
       `auth_user`.`is_active`, 
       `auth_user`.`is_superuser`, 
       `auth_user`.`last_login`, 
       `auth_user`.`date_joined`, 
       t6.`id`, 
       t6.`username`, 
       t6.`first_name`, 
       t6.`last_name`, 
       t6.`email`, 
       t6.`password`, 
       t6.`is_staff`, 
       t6.`is_active`, 
       t6.`is_superuser`, 
       t6.`last_login`, 
       t6.`date_joined` 
FROM   `djangobb_forum_post` 
       INNER JOIN `djangobb_forum_topic` 
         ON ( `djangobb_forum_post`.`topic_id` = `djangobb_forum_topic`.`id` ) 
       INNER JOIN `djangobb_forum_forum` 
         ON ( `djangobb_forum_topic`.`forum_id` = `djangobb_forum_forum`.`id` ) 
       INNER JOIN `djangobb_forum_category` 
         ON ( `djangobb_forum_forum`.`category_id` = 
              `djangobb_forum_category`.`id` ) 
       INNER JOIN `auth_user` 
         ON ( `djangobb_forum_topic`.`user_id` = `auth_user`.`id` ) 
       INNER JOIN `auth_user` t6 
         ON ( `djangobb_forum_post`.`user_id` = t6.`id` ) 
WHERE  `djangobb_forum_post`.`topic_id` = 377 
ORDER  BY `djangobb_forum_post`.`created` ASC 

Traceback:
File "/home/vu2008/new.gamekuba.ru/kuba/env/src/django/django/core/handlers/base.py" in get_response
  111.                         response = callback(request, *callback_args, **callback_kwargs)
File "/home/vu2008/new.gamekuba.ru/kuba/../kuba/libs/djangobb_forum/util.py" in wrapper
  73.             output = function(request, *args, **kwargs)
File "/home/vu2008/new.gamekuba.ru/kuba/../kuba/libs/djangobb_forum/util.py" in wrapper
  94.             result = func(request, *args, **kwargs)
File "/home/vu2008/new.gamekuba.ru/kuba/../kuba/libs/djangobb_forum/views.py" in search
  191.                             topics_to_exclude |= SQ(topic=post.object.topic)

Exception Type: TypeError at /forum/search/?action=search&keywords=&author=Dante&forum=0&search_in=all&sort_by=0&sort_dir=DESC&show_as=topics&search=%D0%9E%D1%82%D0%BF%D1%80%D0%B0%D0%B2%D0%B8%D1%82%D1%8C
Exception Value: unsupported operand type(s) for |=: 'list' and 'SQ'