Cant GetPoint from a TGraph

ROOT
1

I have a root file, from which I am trying to extract data. From summary->g_GE11-VI-L-CERN-0002_EffGainAvg;1:
I am trying these lines:

TFile *mehdifile = TFile::Open("GainMap_GE11-VI-L-CERN-0002.root");
TGraph*graph1 = (TGraph*)mehdifile -> Get("g_GE11-VI-L-CERN-0002_EffGainAvg");
Double_t x;
Double_t y;
graph1 -> GetPoint(0,x,y);

After the last line everything crashes. Can you help me?

GainMap_GE11-VI-L-CERN-0002.root (1.4 MB)

_ROOT Version:_6.12/06
Platform: Not Provided
Compiler: Not Provided

2 
{
  TFile *mehdifile = TFile::Open("GainMap_GE11-VI-L-CERN-0002.root");
  // mehdifile->ls();
  // mehdifile->GetDirectory("Summary")->ls();
  TGraphErrors *graph1;
  mehdifile->GetObject("Summary/g_GE11-VI-L-CERN-0002_EffGainAvg", graph1);
  Double_t x, y;
  graph1->GetPoint(0, x, y);
  std::cout << x << " " << y << std::endl;
}

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