Simplify EmptyCollection(). Thanks, Wolf Behrenhoff!

core/cont/src/TCollection.cxx

@@ -815,8 +815,8 @@ TIter TIter::End()
 
 const TCollection &ROOT::Internal::EmptyCollection()
 {
-   static std::unique_ptr<TCollection> fgEmptyCollection((TCollection *)TClass::GetClass("TObjArray")->New());
-   return *fgEmptyCollection.get();
+   static TObjArray sEmpty;
+   return sEmpty;
 }
 
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