typo for handling translated strings

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21586 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
"os" is not defined

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@21587 4ae1f11a-8b86-4847-b8af-ab372f36d1fd