message: clarify logic in VTK reader
diff: @@ -786,17 +786,13 @@ void Mesh::ReadVTKMesh(std::istream &input, int &curved, int &read_gf,
  MFEM_ABORT("VTK mesh is not in ASCII format!");
  return;
  }
  - buff = "";
  - while (buff == "") // allow blanklines
  + do
  {
  getline(input, buff);
  filter_dos(buff);
  + if (!input.good()) { MFEM_ABORT("VTK mesh is not UNSTRUCTURED_GRID!"); }
  }
  - if (buff != "DATASET UNSTRUCTURED_GRID")
  - {
  - MFEM_ABORT("VTK mesh is not UNSTRUCTURED_GRID!");
  - return;
  - }
  + while (buff != "DATASET UNSTRUCTURED_GRID");
  // Read the points, skipping optional sections such as the FIELD data from
  // VisIt's VTK export (or from Mesh::PrintVTK with field_data==1).
  @@ -860,11 +856,9 @@ void Mesh::ReadVTKMesh(std::istream &input, int &curved, int &read_gf,
  input >> ws >> buff;
  Array<int> cell_types;
  int ncells;
  - if (buff == "CELL_TYPES")
  - {
  + MFEM_VERIFY(buff == "CELL_TYPES", "CELL_TYPES not provided in VTK mesh.")
  input >> ncells;
  cell_types.Load(ncells, input);
  - }
  while ((input.good()) && (buff != "CELL_DATA"))
  {
  