message: Operator: fix error from mfem 4.0 merge.
diff: @@ -44,7 +44,6 @@ void Operator::FormLinearSystem(const Array<int> &ess_tdof_list,
  // rap, X and B point to the same data as this, x and b, respectively
  X.NewMemoryAndSize(x.GetMemory(), x.Size(), false);
  B.NewMemoryAndSize(b.GetMemory(), b.Size(), false);
  - rap = this;
  }
  if (!copy_interior) { X.SetSubVectorComplement(ess_tdof_list, 0.0); }
  