message: Fix a few issues in DeviceConformingProlongationOperator.
diff: @@ -3281,7 +3281,8 @@ static void SetSubVector(const int N,
  const Array<int> &indices,
  const Vector &in, Vector &out)
  {
  - auto y = out.Write();
  + // Use ReadWrite() since we modify only a sebset of the indices:
  + auto y = out.ReadWrite();
  const auto x = in.Read();
  const auto I = indices.Read();
  MFEM_FORALL(i, N, y[I[i]] = x[i];);
  @@ -3310,6 +3311,7 @@ void DeviceConformingProlongationOperator::Mult(const Vector &x,
  int req_counter = 0;
  if (local)
  {
  + y.UseDevice(true);
  y = 0.0;
  }
  else
  @@ -3378,7 +3380,7 @@ static void AddSubVector(const int num_unique_dst_indices,
  const Vector &src,
  Vector &dst)
  {
  - auto y = dst.Write();
  + auto y = dst.ReadWrite();
  const auto x = src.Read();
  const auto DST_I = unique_dst_indices.Read();
  const auto SRC_O = unique_to_src_offsets.Read();
  