[DPG] Fix track from which to compute the signal (#9657)

Author: njacazio

DPG/Tasks/AOTTrack/PID/ITS/qaPIDITS.cxx

@@ -313,8 +313,8 @@ struct itsPidQa {
       histos.fill(HIST("event/pt"), track.pt());
       histos.fill(HIST("event/p"), track.p());
       const auto& t = tracks.iteratorAt(nTracks);
-      histos.fill(HIST("event/averageClusterSize"), track.pt(), averageClusterSizeTrk(t));
-      histos.fill(HIST("event/averageClusterSizePerCoslInv"), track.pt(), averageClusterSizePerCoslInv(t));
+      histos.fill(HIST("event/averageClusterSize"), track.pt(), averageClusterSizeTrk(track));
+      histos.fill(HIST("event/averageClusterSizePerCoslInv"), track.pt(), averageClusterSizePerCoslInv(track));
       bool discard = false;
       for (int id = 0; id < 9; id++) {
         if (std::abs(nsigmaTPC(track, id)) > tpcSelValues[id]) {
@@ -327,8 +327,8 @@ struct itsPidQa {
       if (discard) {
         continue;
       }
-      histos.fill(HIST("event/SelectedAverageClusterSize"), track.pt(), averageClusterSizeTrk(t));
-      histos.fill(HIST("event/SelectedAverageClusterSizePerCoslInv"), track.pt(), averageClusterSizePerCoslInv(t));
+      histos.fill(HIST("event/SelectedAverageClusterSize"), track.pt(), averageClusterSizeTrk(track));
+      histos.fill(HIST("event/SelectedAverageClusterSizePerCoslInv"), track.pt(), averageClusterSizePerCoslInv(track));
 
       for (o2::track::PID::ID id = 0; id <= o2::track::PID::Last; id++) {
         if (!enableParticle[id]) {