message: null initialize Filter::request_headers_ member
  Add missing null initialization of Filter::request_headers_ member introduced in
  Risk Level: Low
  Testing: n/a
diff: @@ -138,7 +138,7 @@ private:
  Upstream::ClusterInfoConstSharedPtr cluster_;
  bool initiating_call_{};
  Http::HeaderMapPtr response_headers_to_add_;
  - Http::HeaderMap* request_headers_;
  + Http::HeaderMap* request_headers_{};
  };
  } // namespace RateLimitFilter
  