Erro Slim Model Cart

[luacarol]

Como estava encontrando problemas em cada aula do curso, resolve pegar a aplicação pronta através do Git, mas mesmo assim eu encontro erros, não faz sentido pois está tudo idêntico.

Slim Application Error
The application could not run because of the following error:

Details
Code: 8
Message: Undefined index: idcart
File: C:\ecommerce-master\vendor\hcodebr\php-classes\src\Model\Cart.php
Line: 20
Trace
#0 C:\ecommerce-master\vendor\hcodebr\php-classes\src\Model\Cart.php(20): Slim\Slim::handleErrors(8, 'Undefined index...', 'C:\ecommerce-ma...', 20, Array)
#1 C:\ecommerce-master\site.php(70): Hcode\Model\Cart::getFromSession()
#2 [internal function]: {closure}()
#3 C:\ecommerce-master\vendor\slim\slim\Slim\Router.php(200): call_user_func_array(Object(Closure), Array)
#4 C:\ecommerce-master\vendor\slim\slim\Slim\Slim.php(1210): Slim\Router->dispatch(Object(Slim\Route))
#5 C:\ecommerce-master\vendor\slim\slim\Slim\Middleware\Flash.php(86): Slim\Slim->call()
#6 C:\ecommerce-master\vendor\slim\slim\Slim\Middleware\MethodOverride.php(94): Slim\Middleware\Flash->call()
#7 C:\ecommerce-master\vendor\slim\slim\Slim\Middleware\PrettyExceptions.php(67): Slim\Middleware\MethodOverride->call()
#8 C:\ecommerce-master\vendor\slim\slim\Slim\Slim.php(1159): Slim\Middleware\PrettyExceptions->call()
#9 C:\ecommerce-master\index.php(19): Slim\Slim->run()
#10 {main}