fix crashes in CbmKFParticleFinderQa when no MC data is presnt

reco/KF/CbmKFParticleFinderQa.cxx

@@ -84,6 +84,8 @@ CbmKFParticleFinderQa::~CbmKFParticleFinderQa()
 
 InitStatus CbmKFParticleFinderQa::Init()
 {
+  fIsInitialized = false;
+
   //Get ROOT Manager
   FairRootManager* ioman = FairRootManager::Instance();
 
@@ -92,6 +94,8 @@ InitStatus CbmKFParticleFinderQa::Init()
     return kERROR;
   }
 
+  fIsInitialized = false;
+
   // check the mode
   fLegacyEventMode = 0;
   if (!ioman->CheckBranch("CbmEvent") && ioman->CheckBranch("MCTrack")) {
@@ -100,10 +104,10 @@ InitStatus CbmKFParticleFinderQa::Init()
 
   // MC Tracks
   if (!fLegacyEventMode) {
-    FairRootManager* fManger    = FairRootManager::Instance();
-    CbmMCDataManager* mcManager = (CbmMCDataManager*) fManger->GetObject("MCDataManager");
+    CbmMCDataManager* mcManager = (CbmMCDataManager*) ioman->GetObject("MCDataManager");
     if (mcManager == nullptr) {
       Error("CbmKFParticleFinderQa::Init", "MC Data Manager not found!");
+      return kSUCCESS;
     }
 
     fMCTrackArray = mcManager->InitBranch("MCTrack");
@@ -126,13 +130,17 @@ InitStatus CbmKFParticleFinderQa::Init()
   }
   else {
     fMCTrackArrayEvent = (TClonesArray*) ioman->GetObject("MCTrack");
+    if (fMCTrackArrayEvent == nullptr) {
+      Error("CbmKFParticleFinderQa::Init", "mc track array not found!");
+      return kSUCCESS;
+    }
   }
 
   // Track match
   fTrackMatchArray = (TClonesArray*) ioman->GetObject("StsTrackMatch");
   if (fTrackMatchArray == nullptr) {
     Error("CbmKFParticleFinderQa::Init", "track match array not found!");
-    return kERROR;
+    return kSUCCESS;
   }
 
   if (fSaveParticles) {
@@ -151,11 +159,18 @@ InitStatus CbmKFParticleFinderQa::Init()
     ioman->Register("KFParticleMatch", "KFParticle", fMatchParticles, IsOutputBranchPersistent("KFParticleMatch"));
   }
 
+  fIsInitialized = true;
+
   return kSUCCESS;
 }
 
 void CbmKFParticleFinderQa::Exec(Option_t* /*opt*/)
 {
+  if (!fIsInitialized) {
+    LOG(warning) << GetName() << " The task can not run! Some data is missing.";
+    return;
+  }
+
   if (fSuperEventAnalysis) {
     LOG(error) << GetName() << " SuperEventAnalysis option currently doesn't work";
     return;
@@ -169,20 +184,23 @@ void CbmKFParticleFinderQa::Exec(Option_t* /*opt*/)
     fMatchParticles->Delete();
   }
 
+  if (!fMcEventList) {
+    return;
+  }
+
   // make sure that the number of events in time slice is 1
 
   int nRecoEvents = 1;
   int nMCEvents   = 1;
 
   if (!fLegacyEventMode) {
-    if (fRecoEvents) {
-      nRecoEvents = fRecoEvents->GetEntriesFast();
-    }
-    nMCEvents = fMcEventList->GetNofEvents();
+    nRecoEvents = (fRecoEvents) ? fRecoEvents->GetEntriesFast() : 0;
+    nMCEvents   = (fMcEventList) ? fMcEventList->GetNofEvents() : 0;
   }
 
   if (nMCEvents != 1 || nRecoEvents != 1) {
-    LOG(warning) << GetName() << " the task doesn't properly work with more than one event in the time slice";
+    LOG(warning) << GetName() << " The task currently doesn't work with more than one event in the time slice";
+    return;
   }
 
   vector<KFMCTrack> mcTracks;

reco/KF/CbmKFParticleFinderQa.h

@@ -57,6 +57,11 @@ class CbmKFParticleFinderQa : public FairTask {
   void FitDecayQAHistograms(float sigma[14], const bool saveReferenceResults = false) const;
   void CheckDecayQA();
 
+
+  // Data members -----------------------
+
+  bool fIsInitialized{false};  // flag for initialization
+
   //input branches
   TClonesArray* fRecoEvents{nullptr};      //! Array of CbmEvent objects
   CbmMCDataArray* fMCTrackArray{nullptr};  //mc tracks

[Anna Senger]

Please check https://redmine.cbm.gsi.de/issues/3439 The code runs without problems, but only for event-by-event reconstruction with MC the histograms are filled