Notice: Undefined property: Config \ App :: $ cookieSameSite

Hello.

Why appears this notice?

Notice: Undefined property: Config\App::$cookieSameSite in C:\xampp\r_crm\vendor\codeigniter4\codeigniter4\system\HTTP\Response.php on line 168

Tested on my local machine. Xampp, Spark, it is in both.

I was fix it by adding this line to App.php
public $cookieSameSite = '';

But I don't understand what's happening at all.
Help me, please.

PS. Solution from https://forum.codeigniter.com/thread-765...ieSameSite doesn't work.

PSS. I found this site with same notice - https://www.qio.kr/