message: fix vector size in MG
diff: @@ -781,9 +781,9 @@ void AbstractMultigrid::MG_Cycle(int level) const
  if (level == P_.Size()) { return; }
  // Coarse grid correction
  - cor_cor_.SetSize(resid_[level].Size());
  P_[level]->MultTranspose(resid_[level], resid_[level+1]);
  MG_Cycle(level+1);
  + cor_cor_.SetSize(resid_[level].Size());
  P_[level]->Mult(correct_[level+1], cor_cor_);
  correct_[level] += cor_cor_;
  op_l->Mult(-1.0, cor_cor_, 1.0, resid_[level]);
  