Avoid leak when stopping server

If accept fails, e.g., because the server is no longer listening the
connection object is not terminated and it results in a memory leak:
connection -> handler -> connection.

websocketpp/roles/server_endpoint.hpp

@@ -104,7 +104,13 @@ public:
             endpoint_type::m_elog.write(log::elevel::rerror,
                 "start_accept error: "+ec.message());
         }
-    }
+		
+		if (ec) {
+			// Terminate the connection to prevent memory leaks.
+			lib::error_code con_ec;
+			con->terminate(con_ec);
+		}
+	}
 
     void handle_accept(connection_ptr con, lib::error_code const & ec) {
         if (ec) {