message: fix seg fault if hist does not exist
diff: @@ -211,13 +211,14 @@ public:
  template<typename T = RootHist_t, typename std::enable_if<std::is_base_of<THnSparse, T>::value>::type* dummy = nullptr>
  double GetSize(double fillFraction = 1.)
  {
  + if(!fRawHist) return 0.;
  double nbinsTotal = 1.;
  for (Int_t d = 0; d < fRawHist->GetNdimensions(); ++d)
  nbinsTotal *= fRawHist->GetAxis(d)->GetNbins() + 2;
  Double_t overhead = 4.; // probably often less; unfortunatley cannot access fRawHist->GetCompactCoord()->GetBufferSize();
  - return (!fRawHist) ? 0. : fillFraction * nbinsTotal * (GetBaseElementSize(fRawHist) + overhead + ((fRawHist->GetSumw2() != -1.) ? sizeof(double) : 0.));
  + return fillFraction * nbinsTotal * (GetBaseElementSize(fRawHist) + overhead + ((fRawHist->GetSumw2() != -1.) ? sizeof(double) : 0.));
  }
  private:
  