bibdocfile: no file streaming for empty records
bibdocfile: no file streaming for empty records

* Do not allow streaming of full-text files for potentially empty records
  (awaiting integration via old WebSubmit technique) or for deleted records.

inveniosoftware/invenio-records,tiborsimko/invenio-records,inveniosoftware/invenio-records,inveniosoftware/invenio-search,inveniosoftware/invenio-search,tiborsimko/invenio-records,tiborsimko/invenio-search,tiborsimko/invenio-search