Codeigniter 4 Websockets Error

I ran into an error while using websockets on my project for the first time.
Everything works fine until I got into an error while connecting clients to the web socket server.

Code:

Running server on host 127.0.0.1:8282
Authentication activated
Running server on host 127.0.0.1:8282
New client connected as (162)
Client (162) authentication success
An error has occurred: Undefined property: Takielias\CodeigniterWebsocket\Libraries\CodeigniterWebsocket::$jwt_key

What's causing the error and how to fix please?