BibDocFile: undefined variable fix
BibDocFile: undefined variable fix

* Fixes internal server error when directories are missing on the
  filesystem.

* Applies fix from 'pu' to 'master'. The fix was overwritten by the recent
  large master to next merge (eefac3e73d8dd5b7c5ac1a47cb298431f4a8662f).

Signed-off-by: Lars Holm Nielsen <7eaffca9f7cd98839b5821d0d23e09ff764b82cd@cern.ch>
Reviewed-by: Jiri Kuncar <2bdffcb416fed3002465740d19a053a39918cbe5@cern.ch>

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