rowCount() is not a suitable way to determine success here, fixes #4158


git-svn-id: svn://develop.studip.de/studip/trunk@29297 c5b85792-5220-0410-ad23-ed5b6b8ad999
fixes #4125, changes based on dabraham

git-svn-id: svn://develop.studip.de/studip/trunk@29299 c5b85792-5220-0410-ad23-ed5b6b8ad999