catch the case where a user doesn't have a default project set... this shouldn't happen but may happen with old DB data

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@1604 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9