message: Add generator event header setting
  needed for running AOD filtering without errors
diff: @@ -312,8 +312,16 @@ void AliGenPerformance::Generate() {
  naccepted++;
  }
  }
  - // AliGenEventHeader* header = new AliGenEventHeader("THn");
  - //gAlice->SetGenEventHeader(header);
  +
  + // Passes header either to the container or to gAlice
  + AliGenEventHeader* header = new AliGenEventHeader("THn");
  + if (fContainer) {
  + header->SetName(fName);
  + fContainer->AddHeader(header);
  + } else {
  + gAlice->SetGenEventHeader(header);
  + }
  +
  if (fStreamer){ // in standard simulation destructor of the streamer (and file->Close() is not called - force writing)
  ((*fStreamer)<<"testGener").GetTree()->Write();
  fStreamer->GetFile()->Flush();
  