…` (elementaire)This PR was merged into the 6.3 branch.Discussion----------[HttpKernel] Handle nullable callback of `StreamedResponse`| Q             | A| ------------- | ---| Branch?       | 6.3| Bug fix?      | yes| New feature?  | no| Deprecations? | no| Tickets       |  -| License       | MITThis PR fixes a bug introduced by#51396. Having a callback in `StreamResponsed` is not a mandatory by design.So the method `getCallback` must check it like `sendContent` does.When we are dealing with cacheable ressource, only headers are sent from `StreamResponsed`, for example:```php#[Route(path: '/download')]public function download(Request $request): StreamedResponse{    // Get the last modified of a file.    $lastModified = \DateTime::createFromFormat('d/m/Y H:i:s', '10/10/2023 13:22:00');    $response = (new StreamedResponse())->setLastModified($lastModified);    if ($response->isNotModified($request)) {        return $response;    }    // Get the stream of a file and attach it to the callback.    // ...    return $response;}````HttpKernel` class have to handle it else if you obtain `HTTP 500` with message `Value of type null is not callable`.cc `@nicolas`-grekasCommits-------66648c5 [HttpKernel] Handle nullable callback of StreamedResponse