littrack: Add gFile + gDirectory protection

reco/littrack/cbm/qa/clustering/CbmLitClusteringQa.cxx

@@ -152,12 +152,18 @@ void CbmLitClusteringQa::Finish() {
 
 void CbmLitClusteringQa::InitMuchGeoScheme(const string& digiFileName) {
   if (fDet.GetDet(ECbmModuleId::kMuch) && fMuchDigiFileName != "") {
-    TFile* oldfile      = gFile;
+    /// Save old global file and folder pointer to avoid messing with FairRoot
+    TFile* oldFile     = gFile;
+    TDirectory* oldDir = gDirectory;
+
     TFile* file         = new TFile(digiFileName.c_str());
     TObjArray* stations = (TObjArray*) file->Get("stations");
     file->Close();
     file->Delete();
-    gFile = oldfile;
+
+    /// Restore old global file and folder pointer to avoid messing with FairRoot
+    gFile      = oldFile;
+    gDirectory = oldDir;
     CbmMuchGeoScheme::Instance()->Init(stations, 0);
   }
 }

reco/littrack/clustering/CbmMuchClustering.cxx

@@ -74,12 +74,19 @@ InitStatus CbmMuchClustering::Init() {
   std::cout << "CbmMuchClustering::Init" << std::endl;
 
   // Initialize GeoScheme
-  TFile* oldfile      = gFile;
+  /// Save old global file and folder pointer to avoid messing with FairRoot
+  TFile* oldFile     = gFile;
+  TDirectory* oldDir = gDirectory;
+
   TFile* file         = new TFile(fDigiFile);
   TObjArray* stations = (TObjArray*) file->Get("stations");
   file->Close();
   file->Delete();
-  gFile = oldfile;
+
+  /// Restore old global file and folder pointer to avoid messing with FairRoot
+  gFile      = oldFile;
+  gDirectory = oldDir;
+
   fScheme->Init(stations, 0);
   // Initialize arrays of objects
   ReadDataBranches();