[11.2.X][clang] Initialize data member to fix clang errors about expl…

…icit deleted def-constructor

backport of cms-sw#32307

PhysicsTools/PatAlgos/plugins/PATTriggerProducer.h

@@ -142,7 +142,7 @@ namespace pat {
         map_[filter].push_back(PathAndFlags(path, pathIndex, lastFilter, l3Filter));
       }
       std::map<std::string, std::vector<PathAndFlags> > map_;
-      const std::vector<PathAndFlags> empty_;
+      const std::vector<PathAndFlags> empty_ = {};
     };
     ModuleLabelToPathAndFlags moduleLabelToPathAndFlags_;
   };