PHP route handler may only return a response object

[tbreuss]

The PHP route handler can return a Response object or an array at the moment: https://github.com/tbreuss/zack/blob/main/src/routing/PhpRouteHandler.php#L13

But HttpKernel expects a Response object and therefore throws an error if we return an array: The controller must return a "Symfony\Component\HttpFoundation\Response" object but it returned an array ([]).

So, the PHP route handler may only return a response object, the appropriate code has to be changed.

[tbreuss]

Fixed with #39