case 2539 - Fix exceptional situation when holdings are not available from backend.
Merge branch 'case-2539' into develop

* case-2539:
  case 2539 - Fix exceptional situation when holdings are not available from backend.
Merge branch 'develop' of github.com:artesis/ding_availability into develop

* 'develop' of github.com:artesis/ding_availability:
  case 2069 - Revert the blackhole field update.
  Review @ Coding Standards.