[PWGDQ] Fix bug: no AssocsCorrectBarrel entries for single MC tracks (#12922)

Co-authored-by: Yuanjing Ji <yji@lxbk0905.gsi.de>
Co-authored-by: Yuanjing Ji <yji@lxbk1130.gsi.de>

Author: 3 people

PWGDQ/Tasks/dqEfficiency_withAssoc.cxx

@@ -607,10 +607,8 @@ struct AnalysisTrackSelection {
       VarManager::ResetValues(0, VarManager::kNBarrelTrackVariables);
       // fill event information which might be needed in histograms/cuts that combine track and event properties
       VarManager::FillEvent<TEventFillMap>(event);
-      ReducedMCEvent* eventMC = nullptr;
       if (event.has_reducedMCevent()) {
-        auto eventMC = event.reducedMCevent();
-        VarManager::FillEvent<VarManager::ObjTypes::ReducedEventMC>(eventMC);
+        VarManager::FillEvent<VarManager::ObjTypes::ReducedEventMC>(event.reducedMCevent());
       }
 
       auto track = assoc.template reducedtrack_as<TTracks>();
@@ -622,8 +620,8 @@ struct AnalysisTrackSelection {
       if (track.has_reducedMCTrack()) {
         auto trackMC = track.reducedMCTrack();
         auto eventMCfromTrack = trackMC.reducedMCevent();
-        if (eventMC != nullptr) {
-          isCorrectAssoc = (eventMCfromTrack.globalIndex() == eventMC->globalIndex());
+        if (event.has_reducedMCevent()) {
+          isCorrectAssoc = (eventMCfromTrack.globalIndex() == event.reducedMCevent().globalIndex());
         }
         VarManager::FillTrackMC(tracksMC, trackMC);
       }