Request\json crashes on empty request body

[Arteneko]

If someone tries to do a Siler\Http\Request\json() when the request body is empty, the json_decode will fail (and return null), and the array type enforcing will fail, thus throwing a TypeError.

An example message is:

Fatal error: Uncaught TypeError: Return value of Siler\Http\Request\json() must be of the type array, null returned

[leocavalcante]

Thanks for reporting!