message: Bugfix: use TransposeMult instead of Mult
diff: @@ -1771,7 +1771,7 @@ void MixedBilinearForm::FormRectangularSystemMatrix(
  }
  else if (test_P)
  {
  - SparseMatrix *m = mfem::Mult(*test_P, *mat);
  + SparseMatrix *m = TransposeMult(*test_P, *mat);
  delete mat;
  mat = m;
  }
  