message: Initialize NCCL communicator in NcclManager::CommunicatorMember.
diff: @@ -74,8 +74,8 @@ struct NcclManager::CommunicatorMember {
  ~CommunicatorMember() {
  if (nccl_comm != nullptr) ncclCommDestroy(nccl_comm);
  }
  - ncclComm_t nccl_comm;
  + ncclComm_t nccl_comm = nullptr;
  // Owned by NcclManager::device_to_comm_streams_.
  NcclStream* nccl_stream = nullptr;
  };
  