Disable sessions file creation on ci4

My code igniter 4 is creating a session file for each access. And its no deleting it.

How can i avoid those files to be created? The documentation doesnt say anything about it.

I have put some code on .env file but didnt work. I have set the folder to NULL but it created a folder called "NULL" lol.

Code:

app.sessionDriver = 'CodeIgniter\Session\Handlers\FileHandler'
app.sessionCookieName = 'ci_session'
app.sessionSavePath = NULL
app.sessionMatchIP = true
app.sessionTimeToUpdate = 0
app.sessionRegenerateDestroy = true

Thanks