fixes #3227
Prevent empty select-box

git-svn-id: svn://develop.studip.de/studip/trunk@25301 c5b85792-5220-0410-ad23-ed5b6b8ad999
fixes #3228 : fix migration

git-svn-id: svn://develop.studip.de/studip/trunk@25302 c5b85792-5220-0410-ad23-ed5b6b8ad999
refine pagination due to bugs in chrome, re #3207

git-svn-id: svn://develop.studip.de/studip/trunk@25303 c5b85792-5220-0410-ad23-ed5b6b8ad999