refs #3239, add a check before fetching a topic blindly from the db

git-svn-id: svn://develop.studip.de/studip/trunk@25869 c5b85792-5220-0410-ad23-ed5b6b8ad999
refs #3239 - remove check temporarily, we are not quite done yet

git-svn-id: svn://develop.studip.de/studip/trunk@25870 c5b85792-5220-0410-ad23-ed5b6b8ad999