fix empty vcf-cards fixes #4186

git-svn-id: svn://develop.studip.de/studip/trunk@29353 c5b85792-5220-0410-ad23-ed5b6b8ad999
refs #3857

fix migration, but still there is a bug in the plus-page

git-svn-id: svn://develop.studip.de/studip/trunk@29354 c5b85792-5220-0410-ad23-ed5b6b8ad999
seminar grouping: fix 'seminar appears multiple times when grouping = semester' problem (+ some code hygiene while i'm at it), fixes #4187

git-svn-id: svn://develop.studip.de/studip/trunk@29355 c5b85792-5220-0410-ad23-ed5b6b8ad999
refs #3857

fix course-navigation

git-svn-id: svn://develop.studip.de/studip/trunk@29356 c5b85792-5220-0410-ad23-ed5b6b8ad999