message: fix treatment of B=0 track extrapolation X estimates
diff: @@ -2877,7 +2877,7 @@ Bool_t AliExternalTrackParam::GetXatLabR(Double_t r,Double_t &x, Double_t bz, In
  if (sn>0) {if (fy>det) return kFALSE;} // track is along Y axis and above the circle
  else {if (fy<-det) return kFALSE;} // track is against Y axis amd belo the circle
  }
  - else if(dir>0) { // agains track direction
  + else if (dir<0) { // agains track direction
  if (sn>0) {if (fy<-det) return kFALSE;} // track is along Y axis
  else if (fy>det) return kFALSE; // track is against Y axis
  }
  