message: prevent seg fault in ->Particle(
diff: @@ -800,10 +800,13 @@ Bool_t AliAnalysisTaskSigmaPlToProtonPiZero::IsRealPhoton(AliAODConversionPhoton
  TParticle *Photon = NULL;
  if (PhotonCandidate.GetNCaloPhotonMCLabels() > 0){
  // Photon = PhotonCandidate.GetMCParticle(fMCEvent);
  + if (PhotonCandidate.GetCaloPhotonMCLabel(0) < 0) return kFALSE;
  Photon = fMCEvent->Particle(PhotonCandidate.GetCaloPhotonMCLabel(0));
  if (Photon) {
  if(Photon->GetPdgCode() == 22){
  + if (Photon->GetMother(0) < 0) return kFALSE;
  TParticle* motherPart2 = (TParticle*)fMCEvent->Particle(Photon->GetMother(0));
  + if (motherPart2->GetMother(0) < 0) return kFALSE;
  TParticle* grandmotherPart2 = (TParticle*)fMCEvent->Particle(motherPart2->GetMother(0));
  if(motherPart2->GetPdgCode() == 111 && grandmotherPart2->GetPdgCode() == 3222){
  return kTRUE;
  @@ -811,8 +814,11 @@ Bool_t AliAnalysisTaskSigmaPlToProtonPiZero::IsRealPhoton(AliAODConversionPhoton
  return kFALSE;
  }
  } else if(Photon->GetPdgCode() == 11 || Photon->GetPdgCode() == -11){
  + if (Photon->GetMother(0) < 0) return kFALSE;
  TParticle* motherPart2 = (TParticle*)fMCEvent->Particle(Photon->GetMother(0));
  + if (motherPart2->GetMother(0) < 0) return kFALSE;
  TParticle* grandmotherPart2 = (TParticle*)fMCEvent->Particle(motherPart2->GetMother(0));
  + if (grandmotherPart2->GetMother(0) < 0) return kFALSE;
  TParticle* grandgrandmotherPart2 = (TParticle*)fMCEvent->Particle(grandmotherPart2->GetMother(0));
  if(motherPart2->GetPdgCode() == 22 && grandmotherPart2->GetPdgCode() == 111 && grandgrandmotherPart2->GetPdgCode() == 3222){
  return kTRUE;
  