Fatal Error if "Excluded Boards" is empty/not numeric

Fatal error: Invalid SQL: SELECT thread.threadID FROM wbb1_1_thread thread WHERE boardID IN(1,2,3,4,5,6,7,8,9) AND boardID NOT IN () AND isDisabled = 0 AND movedThreadID = 0 ORDER BY thread.lastPostTime DESC LIMIT 5

You get more information about the problem in our knowledge base: http://www.woltlab.com/help/?code=1064
Information:

error message: Invalid SQL: SELECT thread.threadID FROM wbb1_1_thread thread WHERE boardID IN(1,2,3,4,5,6,7,8,9) AND boardID NOT IN () AND isDisabled = 0 AND movedThreadID = 0 ORDER BY thread.lastPostTime DESC LIMIT 5
error code: 1064
sql type: MySQLDatabase
sql error: 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 ') AND isDisabled = 0 AND movedThreadID = 0 ORDER BY thread.lastPostTime DESC ' at line 3
sql error number: 1064
sql version:
file: /var/customers/webs/tecboys/wcf/lib/system/database/MySQLDatabase.class.php (118)
php version: 5.3.20-1~dotdeb.0
wcf version: 1.1.9 (Tempest)
date: Wed, 06 Feb 2013 18:56:13 +0000
request: /index.php?page=Start
referer: http://www.tecboy-gaming.de/index.php?page=Portal
Stacktrace:
#0 /var/customers/webs/tecboys/lib/data/thread/ThreadList.class.php(68): MySQLDatabase->sendQuery('SELECT??thread....', 5, 0)
#1 /var/customers/webs/tecboys/lib/data/thread/ThreadList.class.php(80): ThreadList->readThreadIDs()
#2 /var/customers/webs/tecboys/lib/system/event/listener/boxes/StartPagePostsBoxListener.class.php(19): ThreadList->readThreads()
#3 /var/customers/webs/tecboys/lib/system/event/listener/boxes/StartPagePostsBoxListener.class.php(24): StartPagePostsBoxListener->getThreads()
#4 /var/customers/webs/tecboys/wcf/lib/system/event/EventHandler.class.php(207): StartPagePostsBoxListener->execute(Object(StartPage), 'StartPage', 'assignVariables')
#5 /var/customers/webs/tecboys/wcf/lib/page/AbstractPage.class.php(73): EventHandler::fireAction(Object(StartPage), 'assignVariables')
#6 /var/customers/webs/tecboys/lib/page/StartPage.class.php(43): AbstractPage->assignVariables()
#7 /var/customers/webs/tecboys/wcf/lib/page/AbstractPage.class.php(93): StartPage->assignVariables()
#8 /var/customers/webs/tecboys/wcf/lib/page/AbstractPage.class.php(46): AbstractPage->show()
#9 /var/customers/webs/tecboys/wcf/lib/util/RequestHandler.class.php(64): AbstractPage->__construct()
#10 /var/customers/webs/tecboys/wcf/lib/util/RequestHandler.class.php(92): RequestHandler->__construct('Start', Array, 'page')
#11 /var/customers/webs/tecboys/index.php(8): RequestHandler::handle(Array)
#12 {main}