search: fix get_record with only reserved recid
search: fix get_record with only reserved recid

* Fixes problem with creating MARC representation of a record when
  only recid is reserved.

Co-authored-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>
Signed-off-by: Eamonn Maguire <96b6f94f66c06f69bd75d8dd0685c723c866c621@cern.ch>

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