Masalah ketika CRUD dan login menggunakan framework sendiri

Pesan error begini

Fatal error: Uncaught Error: Call to a member function login() on null in C:\xampp\htdocs\Revianime\app\controllers\Login.php:14 Stack trace: #0 C:\xampp\htdocs\Revianime\app\core\App.php(20): Login->login() #1 C:\xampp\htdocs\Revianime\public\index.php(6): App->__construct() #2 {main} thrown in C:\xampp\htdocs\Revianime\app\controllers\Login.php on line 14