bibdocfile: fixed CLI --append bug
bibdocfile: fixed CLI --append bug

* Fixed bug in bibdocfile CLI --append where it was impossible to
  append a document to a record that didn't already had documents.

* Removed a forgotten debug directive.

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