Null value for response on delete

[Apen-nootjes]

Somehow I can't create a branch and pull request to you guys (probably my mistake). But when you do a DELETE call, the response will be NULL, so you will get an error on line 63, since $this->response must be an array at this time.

I would like to suggest to allow for null values there. So:

On line 16, change to:

protected array|null $responsel;

On line 161, change to:

public function getResponse() : ?array

Would be awsome if you can add this.