WebStyle: fix legacy form values unicode issue
WebStyle: fix legacy form values unicode issue

* Fixes bug related to converting form values from unicode to str
  for legacy applications.

Reviewed-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio,tiborsimko/invenio