forum: prevent empty category names on edit, fixes #3386

git-svn-id: svn://develop.studip.de/studip/trunk@26050 c5b85792-5220-0410-ad23-ed5b6b8ad999
forum: prevent empty category names on edit, fixes #3386

git-svn-id: svn://develop.studip.de/studip/trunk@26051 c5b85792-5220-0410-ad23-ed5b6b8ad999