[DPG] Fix multiple initialisations in histogram registry (#8924)

Author: lbariogl

DPG/Tasks/AOTTrack/qaEfficiency.cxx

@@ -338,7 +338,6 @@ struct QaEfficiency {
                                   phiMin, phiMax,
                                   yMin, yMax);
     const int histogramIndex = id + pdgSign * nSpecies;
-    hPtmotherGenerated = histos.add<TH1>("MC/mother/pt/generated", "Generated pT of mother Lambda or Xi", kTH1D, {axisPt});
 
     // Pt
     hPtIts[histogramIndex] = histos.add<TH1>(Form("MC/pdg%i/pt/its", PDGs[histogramIndex]), "ITS tracks " + tagPt, kTH1D, {axisPt});
@@ -664,6 +663,9 @@ struct QaEfficiency {
       histos.add("MC/occ_cent/reco/neg/its", "ITS Negative ", kTH3D, {axisOcc, axisCent, axisPt});
     }
 
+    AxisSpec axisPtMother{ptBins, "#it{p}_{T} (GeV/#it{c})"};
+    hPtmotherGenerated = histos.add<TH1>("MC/mother/pt/generated", "Generated pT of mother Lambda or Xi", kTH1D, {axisPtMother});
+
     static_for<0, 1>([&](auto pdgSign) {
       makeMCHistograms<pdgSign, o2::track::PID::Electron>(doEl);
       makeMCHistograms<pdgSign, o2::track::PID::Muon>(doMu);