Unreasonable default parameter

[JuveLee]

The parameter 'messages' for function CodeIgniter\Controller->validate has a unreasonable default value 'null'.
Beacuse that function call a function CodeIgniter\Validation\Validation->setRules, and the second parameter of that function has a default value 'empty array'.
So when I use validate function like this:
$this->validate($this->request, ['title' => 'required', 'text' => 'required'])
There will be an error "Argument 2 passed to CodeIgniter\Validation\Validation::setRules() must be of the type array, null given".