warning fixes in AnalysisTree

The MR fixes the following warnings (that can be seen here: https://cdash.gsi.de/buildSummary.php?buildid=432309):

===

/home/cbmdock/cbmroot/analysis/common/analysis_tree_converter/CbmFsdHitsConverter.cxx: In member function 'virtual void CbmFsdHitsConverter::ProcessData(CbmEvent*)':
/home/cbmdock/cbmroot/analysis/common/analysis_tree_converter/CbmFsdHitsConverter.cxx:269:22: warning: comparison of integer expressions of different signedness: 'const unsigned int' and 'Int_t' {aka 'int'} [-Wsign-compare]
       if (trackIndex > cbm_global_tracks_->GetEntriesFast()) {
           ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

analysis/common/analysis_tree_converter/CbmFsdHitsConverter.cxx

@@ -265,7 +265,7 @@ void CbmFsdHitsConverter::ProcessData(CbmEvent* event)
     hit.SetField(storedIndex, i_bestMatchedGTrack_);
 
     if ((bestMatchedIndex >= 0) && (bestChi2 > fsdgtrack_minChi2_) && (bestChi2 < fsdgtrack_maxChi2_)) {
-      const auto trackIndex = event ? event->GetIndex(ECbmDataType::kGlobalTrack, bestMatchedIndex) : bestMatchedIndex;
+      const Int_t trackIndex = event ? event->GetIndex(ECbmDataType::kGlobalTrack, bestMatchedIndex) : bestMatchedIndex;
       if (trackIndex > cbm_global_tracks_->GetEntriesFast()) {
         LOG(error) << "Trying to access element " << trackIndex << " which is out ot the global track array of size"
                    << cbm_global_tracks_->GetEntriesFast();