Fix seg fault caused by stale particle indices after coalescence from HF decays (#2416)

Author: alcaliva

MC/config/common/external/generator/CoalescencePythia8.h

@@ -107,6 +107,7 @@ bool doCoal(Pythia8::Event& event, int charge, int pdgCode, float mass, bool tri
 bool CoalescencePythia8(Pythia8::Event& event, std::vector<unsigned int> inputPdgList = {}, bool trivialCoal = false, double coalMomentum = 0.4, int firstDauID = -1, int lastDauId = -1, float maxRapidity = 1.)
 {
   const double coalescenceRadius{0.5 * 1.122462 * coalMomentum};
+
   // if coalescence from a heavy hadron, loop only between firstDauID and lastDauID
   int loopStart = firstDauID > -1 ? firstDauID : 0;
   int loopEnd = lastDauId > -1 ? lastDauId : event.size() - 1;
@@ -143,7 +144,7 @@ bool CoalescencePythia8(Pythia8::Event& event, std::vector<unsigned int> inputPd
       lambdas[event[iPart].id() > 0].push_back(iPart);
     }
   }
-  // run coalescence
+  // Run coalescence
   bool nuclFromDecay = firstDauID > -1;
   bool coalHappened = false;
 
@@ -152,26 +153,41 @@ bool CoalescencePythia8(Pythia8::Event& event, std::vector<unsigned int> inputPd
       for (int iN{0}; iN < neutrons[iC].size(); ++iN) {
         if (nuclearMask & (1 << kDeuteron)) {
           coalHappened |= doCoal(event, iC, pdgList[kDeuteron], massList[kDeuteron], trivialCoal, coalescenceRadius, nuclFromDecay, protons[iC][iP], neutrons[iC][iN]);
+          if (nuclFromDecay && coalHappened) {
+            return true;
+          }
         }
         if (nuclearMask & (1 << kTriton)) {
           for (int iN2{iN + 1}; iN2 < neutrons[iC].size(); ++iN2) {
             coalHappened |= doCoal(event, iC, pdgList[kTriton], massList[kTriton], trivialCoal, coalescenceRadius, nuclFromDecay, protons[iC][iP], neutrons[iC][iN], neutrons[iC][iN2]);
+            if (nuclFromDecay && coalHappened) {
+              return true;
+            }
           }
         }
         if (nuclearMask & (1 << kHe3)) {
           for (int iP2{iP + 1}; iP2 < protons[iC].size(); ++iP2) {
             coalHappened |= doCoal(event, iC, pdgList[kHe3], massList[kHe3], trivialCoal, coalescenceRadius, nuclFromDecay, protons[iC][iP], protons[iC][iP2], neutrons[iC][iN]);
+            if (nuclFromDecay && coalHappened) {
+              return true;
+            }
           }
         }
         if (nuclearMask & (1 << kHyperTriton)) {
           for (int iL{0}; iL < lambdas[iC].size(); ++iL) {
             coalHappened |= doCoal(event, iC, pdgList[kHyperTriton], massList[kHyperTriton], trivialCoal, coalescenceRadius, nuclFromDecay, protons[iC][iP], neutrons[iC][iN], lambdas[iC][iL]);
+            if (nuclFromDecay && coalHappened) {
+              return true;
+            }
           }
         }
         if (nuclearMask & (1 << kHe4)) {
           for (int iP2{iP + 1}; iP2 < protons[iC].size(); ++iP2) {
             for (int iN2{iN + 1}; iN2 < neutrons[iC].size(); ++iN2) {
               coalHappened |= doCoal(event, iC, pdgList[kHe4], massList[kHe4], trivialCoal, coalescenceRadius, nuclFromDecay, protons[iC][iP], protons[iC][iP2], neutrons[iC][iN], neutrons[iC][iN2]);
+              if (nuclFromDecay && coalHappened) {
+                return true;
+              }
             }
           }
         }