Discuz! Database Error

(1064) You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1
SELECT class FROM forum_thread WHERE tid=

PHP Debug

No.FileLineCode
1forum.php67require(%s)
2source/module/forum/forum_forumdisplay.php974include(%s)
3data/template/4_diy_forum_forumdisplay.tpl.php956discuz_database::query(%s)
4source/class/discuz/discuz_database.php142db_driver_mysql->query(%s, false, false)
5source/class/db/db_driver_mysql.php152db_driver_mysql->halt(%s, %d, %s)
6source/class/db/db_driver_mysql.php223break()
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