Fix: tooltip correctly handles the absence of info (empty string)

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16457 85f007b7-540e-0410-9357-904b9bb8a0f7
Fix compilation (vernac.ml, missing ;)

I did forget a ; while dealing with conflicts in git-svn rebase

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16458 85f007b7-540e-0410-9357-904b9bb8a0f7