fix for 0004426: Email notifications to users with language set to "auto" causes errors
use language default if user has selected auto

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@2916 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9