Fix potential memory leak

It is better to init jresp as NULL, and allocate new memory when it is
used, this will avoid the memory leak if the function returns during the
process.

Bug-AGL: SPEC-3584

Change-Id: Icb1eae050294f4438ad89739e324c5483b6b3441
Signed-off-by: Li Xiaoming <lixm.fnst@cn.fujitsu.com>

binding/navigation-api.c

@@ -80,7 +80,7 @@ static void navigation_subscribe_unsubscribe(afb_req_t request,
 		gboolean unsub)
 {
 	struct navigation_state *ns = navigation_get_userdata();
-	json_object *jresp = json_object_new_object();
+	json_object *jresp = NULL;
 	const char *value;
 	afb_event_t event;
 	int rc;
@@ -121,6 +121,7 @@ static void navigation_subscribe_unsubscribe(afb_req_t request,
 		return;
 	}
 
+	jresp = json_object_new_object();
 	afb_req_success_f(request, jresp, "Navigation %s to event \"%s\"",
 			!unsub ? "subscribed" : "unsubscribed",
 			value);