message: Replace `HostReadData` with `Finalized`.
diff: @@ -1497,7 +1497,7 @@ void SparseMatrix::Symmetrize()
  int SparseMatrix::NumNonZeroElems() const
  {
  - if (HostReadData() != NULL) // matrix is finalized
  + if ( Finalized() )
  {
  HostReadI();
  return I[height];
  