BibFormat: fix traceback in bibreformat
BibFormat: fix traceback in bibreformat

* Fixes traceback in bibreformat when no default output argument
  was used.  Also, uses the old full option name for backwards
  compatibility, as before 9dbc767498a44b12f3d4a80d43b8afb8718ef21a.

tiborsimko/invenio-formatter,tiborsimko/invenio-formatter,inveniosoftware/invenio-formatter,inveniosoftware/invenio-formatter,inveniosoftware/invenio-formatter,tiborsimko/invenio-formatter