message: Improve user-friendliness of crashes.
diff: @@ -201,10 +201,18 @@ bool AliEventCuts::AcceptEvent(AliVEvent *ev) {
  if (fCentralityFramework) {
  if (fCentralityFramework == 2) {
  AliCentrality* cent = ev->GetCentrality();
  + if (!cent) {
  + AliFatal("The legacy centrality framework has been request but no AliCentrality object was found attached to the Event."
  + " Did you run the Centrality Framework?");
  + }
  fCentPercentiles[0] = cent->GetCentralityPercentile(fCentEstimators[0].data());
  fCentPercentiles[1] = cent->GetCentralityPercentile(fCentEstimators[1].data());
  } else {
  AliMultSelection* cent = (AliMultSelection*)ev->FindListObject("MultSelection");
  + if (!cent) {
  + AliFatal("The multiplicity selection framework has been request but no AliMultSelection object was found attached to the Event."
  + " Did you run the AliMultSelectionTask?");
  + }
  fCentPercentiles[0] = cent->GetMultiplicityPercentile(fCentEstimators[0].data(), fMultSelectionEvCuts);
  fCentPercentiles[1] = cent->GetMultiplicityPercentile(fCentEstimators[1].data(), fMultSelectionEvCuts);
  }
  