documents: provide appropriate error message if config setting has not been set or is invalid, re #4235

git-svn-id: svn://develop.studip.de/studip/trunk@31106 c5b85792-5220-0410-ad23-ed5b6b8ad999
StEP00249: fix debuties bosses, re #4484

git-svn-id: svn://develop.studip.de/studip/trunk@31107 c5b85792-5220-0410-ad23-ed5b6b8ad999
documents: fix syntax error after merge (and get rid of some <font> tag while i'm at it), re #4235

git-svn-id: svn://develop.studip.de/studip/trunk@31108 c5b85792-5220-0410-ad23-ed5b6b8ad999