Fixes to MUON5 for Upgrade samples

Fixes to MUON5 for Upgrade samples

PhysicsAnalysis/DerivationFramework/DerivationFrameworkMuons/python/MUON5.py

-# Copyright (C) 2002-2023 CERN for the benefit of the ATLAS collaboration
+# Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 #!/usr/bin/env python
 #====================================================================
 # DAOD_MUON5.py
@@ -67,9 +67,15 @@ def MUON5KernelCfg(ConfigFlags, name='MUON5Kernel', **kwargs):
     
     MUON5SkimmingTools = []
     from DerivationFrameworkTools.DerivationFrameworkToolsConfig import xAODStringSkimmingToolCfg
+    # if we are running on upgrade MC (no trigger), we disable the TDT inside the skimming tool. 
+    # The TDT is not actually used as we skim only on offline objects. 
+    SkimArgs={}
+    if  not (ConfigFlags.Reco.EnableTrigger or ConfigFlags.Trigger.triggerConfig == 'INFILE'): 
+        SkimArgs["TrigDecisionTool"] = ""
     MUON5SkimmingTool1 = acc.getPrimaryAndMerge(xAODStringSkimmingToolCfg(ConfigFlags,
                                                                           name       = "MUON5SkimmingTool1",
-                                                                          expression = lepSelection))
+                                                                          expression = lepSelection,
+                                                                          **SkimArgs))
     MUON5SkimmingTools.append(MUON5SkimmingTool1) 
 
     # --------
@@ -94,10 +100,15 @@ def MUON5KernelCfg(ConfigFlags, name='MUON5Kernel', **kwargs):
     from DerivationFrameworkCalo.CaloCellDFGetterConfig import thinCaloCellsForDFCfg
     from DerivationFrameworkMuons.MuonsToolsConfig import AnalysisMuonThinningAlgCfg
     
+    # protect against missing forward tracks in Upgrade 
+    fwdTracks = "InDetForwardTrackParticles"
+    if fwdTracks not in ConfigFlags.Input.Collections:
+        fwdTracks = "" 
     acc.merge(AnalysisMuonThinningAlgCfg(ConfigFlags,
                                          MuonPassFlags = muonThinFlags,
                                          TrkPassFlags = trkThinFlags,
-                                         StreamName = kwargs['StreamName']))
+                                         StreamName = kwargs['StreamName'], 
+                                         IdTrkFwdThinning=fwdTracks))
     
 
     # keep topoclusters around muons

Tracking/TrkVertexFitter/TrkVertexBilloirTools/src/FastVertexFitter.cxx

 /*
-  Copyright (C) 2002-2022 CERN for the benefit of the ATLAS collaboration
+  Copyright (C) 2002-2024 CERN for the benefit of the ATLAS collaboration
 */
 
 /***************************************************************************
@@ -372,10 +372,15 @@ namespace Trk
  		    
  		    
  		   xAOD::Vertex* fittedVertex = fit( measuredPerigees, constraint ); 
- 		 
+ 		   // fit() may return nullptr, need to protect 
+		   if (fittedVertex == nullptr){
+				ATH_MSG_WARNING("Failed fit, returning null vertex"); 
+				return nullptr; 
+		   }
  		   //assigning the input tracks to the fitted vertex through VxTrackAtVertices
  		   { 
  		    if( fittedVertex->vxTrackAtVertexAvailable() ) // TODO: I don't think vxTrackAtVertexAvailable() does the same thing as a null pointer check!
+																							// Regretful Hindsight 8 years later: No, it doesn't! 
  		    { 
  		     if(!fittedVertex->vxTrackAtVertex().empty()) 
  		     {