message: Check that Rendezvous is not null.
diff: @@ -32,6 +32,10 @@ Status SendTensorsToRendezvous(
  "; alloc_attrs.size() = ", alloc_attrs.size());
  }
  + if (!rendezvous) {
  + return errors::InvalidArgument("Rendezvous is null.");
  + }
  +
  Rendezvous::ParsedKey parsed;
  for (int i = 0; i < keys.size(); ++i) {
  Rendezvous::Args rendez_args;
  