message: Add crucial protection for pre-optimization stage
diff: @@ -1807,13 +1807,14 @@ Double_t AliAnalysisTaskWeakDecayVertexer::GetDCAV0Dau( AliExternalTrackParam *p
  TMath::Power(lCase1NegR[2]-lCase1PosR[2],2)
  );
  //Pass coordinates
  - if( lPreprocessDCAxy<1e+3){
  + if( lPreprocessDCAxy<999){
  lPreprocessxp = xThisPos;
  lPreprocessxn = xThisNeg;
  }
  }
  //================================================================
  } else {
  + if( lDist > TMath::Abs(NegRadius-PosRadius) ){ //otherwise this algorithm will fail!
  //================================================================
  //Case 2: distance smaller than sum of radii (cowboy/sailor configs)
  @@ -1916,15 +1917,18 @@ Double_t AliAnalysisTaskWeakDecayVertexer::GetDCAV0Dau( AliExternalTrackParam *p
  lPreprocessxn = lxnLargestR;
  }
  //Protection against something too crazy, please
  - if( lPreprocessDCAxy>1e+3){
  + if( lPreprocessDCAxy>999){
  lPreprocessxp = pt->GetX(); //start at current location
  lPreprocessxn = nt->GetX(); //start at current location
  }
  }
  + }
  //End of preprocessing stage!
  //at this point lPreprocessxp, lPreprocessxn are already good starting points: update helixparams
  + if( lPreprocessDCAxy < 999 ) { //some improvement... otherwise discard in all cases, please
  nt->PropagateTo(lPreprocessxn, b);
  pt->PropagateTo(lPreprocessxp, b);
  + }
  //don't redefine!
  nt->GetHelixParameters(p1,b);
  