Merge branch 'cherry-pick-4af1d5c2 [formerly 1448b8cdc8]-21.1' into '21.1'

Sweeping !14450 from 21.1-dev to 21.1.
Fix bug whereby a histogram plotted twice would be modifed twice

See merge request atlas/athena!14480

Former-commit-id: 2b6b5ea9cf41700257b0d561ceea878916f3a5e9

Trigger/TrigAnalysis/TrigInDetAnalysisUser/Analysis/src/comparitor.cxx

@@ -59,7 +59,6 @@ bool fulldbg = false;
 template<typename T=TH1F>
 T* Get( TFile& f, const std::string& n, const std::string& dir="", std::vector<std::string>* saved=0  ) { 
 
-
   std::string name;
 
   size_t pos = n.find("+");
@@ -80,6 +79,8 @@ T* Get( TFile& f, const std::string& n, const std::string& dir="", std::vector<s
     }
   }
 
+  if ( h ) h->SetDirectory(0);
+
   return h;
 }