message: poplar_executor: Skip some work and logging when there are no send_infos
  Summary: Fixes T20087.
  Test Plan: Tests pass.
  Reviewers: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, georgep
  Maniphest Tasks: T20087
diff: @@ -341,6 +341,10 @@ void PoplarExecutor::Deallocate(se::DeviceMemoryBase* mem) {
  Status PoplarExecutor::ConnectSendCallbacksToRendezvous(
  const SendRecvInfos& send_infos) {
  + if (send_infos.empty()) {
  + return Status::OK();
  + }
  +
  const int64 num_replicas = current_replication_factor_;
  const bool can_buffers_overlap =
  