message: add protection for cocktail weighting
diff: @@ -454,6 +454,9 @@ void AliAnalysisTaskElectronEfficiencyV2::UserCreateOutputObjects(){
  std::cout << "Copy cocktail weighting from Alien" << std::endl;
  fCocktailFile = TFile::Open(fCocktailFilename.c_str());
  }
  + if (!fCocktailFile->IsOpen()) {
  + AliError(Form("Could not open file %s", fCocktailFilename.c_str()));
  + }
  if (fCocktailFile){
  fPtPion = dynamic_cast<TH1F*>(fCocktailFile->Get("Pion"));
  