message: fixes matrix' copy and move assignment
diff: @@ -400,7 +400,6 @@ Matrix<ValueType, LocalIndexType, GlobalIndexType>::operator=(
  gather_idxs_ = other.gather_idxs_;
  send_offsets_ = other.send_offsets_;
  recv_offsets_ = other.recv_offsets_;
  - recv_sizes_ = other.recv_sizes_;
  send_sizes_ = other.send_sizes_;
  recv_sizes_ = other.recv_sizes_;
  non_local_to_global_ = other.non_local_to_global_;
  @@ -425,7 +424,6 @@ Matrix<ValueType, LocalIndexType, GlobalIndexType>::operator=(Matrix&& other)
  gather_idxs_ = std::move(other.gather_idxs_);
  send_offsets_ = std::move(other.send_offsets_);
  recv_offsets_ = std::move(other.recv_offsets_);
  - recv_sizes_ = std::move(other.recv_sizes_);
  send_sizes_ = std::move(other.send_sizes_);
  recv_sizes_ = std::move(other.recv_sizes_);
  non_local_to_global_ = std::move(other.non_local_to_global_);
  