BibRank: citation flip flop

* Fixes an issue that caused dropping citations on re-indexing during
  the journal catchup phase.

Signed-off-by: Daniel Lovasko <daniel.lovasko@cern.ch>
Co-authored-by: Samuele Kaplun <samuele.kaplun@cern.ch>
Can you add a comment why the added "-*" is needed? I would like to know :dancer: