Disabling an HS with service-side rend circs in progress may produce ‘Internal Error’ log message

From rend_service_rendezvous_has_opened:

  service = rend_service_get_by_pk_digest(
                circuit->rend_data->rend_pk_digest);
  if (!service) {
    log_warn(LD_GENERAL, "Internal error: unrecognized service ID on "
             "introduction circuit.");
    reason = END_CIRC_REASON_INTERNAL;
    goto err;
  }

When a hidden service is removed from Tor's configuration, rend_config_services closes its introduction circuits, but not its rendezvous circuits. Leaving in-progress rend circs open can trigger this ‘Internal Error’ log message.