workaround for translations 500

http://manage.dimagi.com/default.asp?111525

this appears to have been introduced by https://github.com/dimagi/commcare-hq/commit/d165581746f82ed19ebb27b189f811223aa6f1e6
which made the incorrect assumption that the result of
`Translation.get_translations` was always a dict. Not knowing why the
change was made, this just works around the error
Merge pull request #3326 from dimagi/case-111525

workaround for translations 500