message: additional protection in case cocktail list exists with 0 entries but main header is available
diff: @@ -1540,7 +1540,8 @@ AliGenPythiaEventHeader * AliMCAnalysisUtils::GetPythiaEventHeader
  else
  {
  ngen = genlist->GetEntries();
  - if( ngen < 1 ) return pyGenHead;
  + if ( ngen < 1 && !mcevent->GenEventHeader() ) return pyGenHead;
  + else ngen = 1 ;
  }
  // printf("GetPythiaEventHeader() - N generators %d, cocktail list %p, gen header %p\n",
  