documents: fix call to download controller constructor, refines [31330], re #4235

git-svn-id: svn://develop.studip.de/studip/trunk@31333 c5b85792-5220-0410-ad23-ed5b6b8ad999
re #4235

don't append cid on download links, if they aren't needed

git-svn-id: svn://develop.studip.de/studip/trunk@31334 c5b85792-5220-0410-ad23-ed5b6b8ad999