message: Capture null pointers in helper function
diff: @@ -2589,13 +2589,17 @@ Bool_t AliMultSelectionTask::PassesTrackletVsCluster(AliVEvent* event)
  //______________________________________________________________________
  Bool_t AliMultSelectionTask::HasGoodVertex2016(AliVEvent* event)
  {
  + if(!event) return kFALSE;
  //Good Vertex according to criteria discussed on the 05th October 2016
  //Adaptation (virtual classes) of snippet from:
  // https://indico.cern.ch/event/489471/contributions/2320075/attachments/1348724/2034963/DPG_PF_20161005.pdf
  Bool_t lReturnValue = kTRUE; //optimisitc: good until proven otherwise
  +
  const AliVVertex* vtTrc = event->GetPrimaryVertex();
  + if(!vtTrc) return kFALSE;
  const AliVVertex* vtSPD = event->GetPrimaryVertexSPD();
  + if(!vtSPD) return kFALSE;
  if (vtTrc->GetNContributors()<2 || vtSPD->GetNContributors()<1) lReturnValue = kFALSE;// one of vertices is missing
  double covTrc[6],covSPD[6];
  vtTrc->GetCovarianceMatrix(covTrc);
  