BibAuthorID: fix for rejection of claimed signatures

* Fixes an issue that makes it impossible to reject already claimed signatures
  or disclaim already rejected signatures by the user or the owner of the
  profile.

Signed-off-by: Artem Tsikiridis <artem.tsikiridis@cern.ch>
Merge pull request #144 from atsikiridis/claimed-rejection-hotfix

BibAuthorID: hotfix for rejection of claimed papers