Warning: Undefined variable $controller in /var/www/rainer.one/app/Core/Router.php on line 256

Fatal error: Uncaught TypeError: call_user_func_array(): Argument #1 ($callback) must be a valid callback, first array member is not a valid class name or object in /var/www/rainer.one/app/Core/Router.php:256 Stack trace: #0 /var/www/rainer.one/app/Core/Router.php(256): call_user_func_array() #1 /var/www/rainer.one/app/Core/helpers/init.php(30): Core\Router->loadController() #2 /var/www/rainer.one/public/index.php(5): require('...') #3 {main} thrown in /var/www/rainer.one/app/Core/Router.php on line 256