fix: Response::download() causes TypeError

[kenjis]

Description Fixes #6358

How to Test

<?php

namespace App\Controllers;

class Home extends BaseController
{
    public function index()
    {
        return $this->response->download('some.txt', 'some text', true);
    }
}

Checklist:

• [x] Securely signed commits
• [] Component(s) with PHPDoc blocks, only if necessary or adds value
• [ ] Unit testing, with >80% coverage
• [ ] User guide updated
• [x] Conforms to style guide

[MGatner]

Should RedirectResponse be checked? Also, I think null is an acceptable body for some API responses - we might need to check or cast that.

[nicojmb]

Hi, same problem here, just testedkenjis fix and works fine.

[kenjis]

Changed the implementation.

[MGatner]

Any ideas how this made it through tests to release?