MT#63324 fix Auth::is_user_banned error

* fix a scenario when $key is undefined because the user
  is authenticating via JWT.

Change-Id: I8d5925e209728d55de7557e9652ee47ea0ea48c1

lib/NGCP/Panel/Utils/Auth.pm

@@ -650,7 +650,7 @@ sub user_is_banned {
         $key = login_ban_subscriber_key($p_user, $p_domain, $realm, $ip, $user_id, $customer_id);
     }
 
-    return $redis->exists($key) ? 1 : 0;
+    return $key ? ($redis->exists($key) ? 1 : 0) : 0;
 }
 
 sub log_failed_login_attempt {