conf+security: accommodate certificate name in KeyLocator

refs #5195

Change-Id: I88709f891fe78fc9f2699bc021d35ca72ebc6850
diff --git a/src/conf-parameter.hpp b/src/conf-parameter.hpp
index 57dd2c2..9989803 100644
--- a/src/conf-parameter.hpp
+++ b/src/conf-parameter.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2021,  The University of Memphis,
+ * Copyright (c) 2014-2022,  The University of Memphis,
  *                           Regents of the University of California,
  *                           Arizona Board of Regents.
  *
@@ -475,7 +475,7 @@
     return m_keyChain;
   }
 
-  std::shared_ptr<ndn::security::Certificate>
+  ndn::optional<ndn::security::Certificate>
   initializeKey();
 
   void