Clear error codes idiomatically

example/http/client/sync-ssl/http_client_sync_ssl.cpp

@@ -111,7 +111,7 @@ int main(int argc, char** argv)
         {
             // Rationale:
             // http://stackoverflow.com/questions/25587403/boost-asio-ssl-async-shutdown-always-finishes-with-an-error
-            ec.assign(0, ec.category());
+            ec = {};
         }
         if(ec)
             throw beast::system_error{ec};