message: In ParMesh::Rebalance(), check for nodes before checking for
  parallel FE space.
diff: @@ -3111,7 +3111,7 @@ void ParMesh::Rebalance()
  sequence++;
  // Make sure the Nodes use a ParFiniteElementSpace
  - if (dynamic_cast<ParFiniteElementSpace*>(Nodes->FESpace()) == NULL)
  + if (Nodes && dynamic_cast<ParFiniteElementSpace*>(Nodes->FESpace()) == NULL)
  {
  ParFiniteElementSpace *pfes =
  new ParFiniteElementSpace(*Nodes->FESpace(), *this);
  