Fix unknown $request variable

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | ~
| License       | MIT
| Doc PR        | ~

Fix the following error:
```php
Fatal error: Call to a member function getUri() on a non-object in /Users/benjamin/Development/mini-scrum/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/HttpContentRenderer.php on line 130
```