Fix 404 error on get_group_users for deleted grappa groups
from this: https://gitlab.cern.ch/push-notifications/notifications-docs/-/issues/5
Deleted Grappa groups are throwing a 404 error in archive and router.
from this: https://gitlab.cern.ch/push-notifications/notifications-docs/-/issues/5
Deleted Grappa groups are throwing a 404 error in archive and router.