Fix non-authenticated users being counted as sessions

[Pacodastre]

…dashboard

[DecDuck]

Does this do anything? userId can't be null.

[Pacodastre]

Not entirely sure why, but the following request

        await prisma.session.groupBy({
          by: ["userId"],
        }),

returns this

[ { userId: null }, { userId: '46d4ebaf-e79d-427e-b3ba-2162dafaeb9a' } ]

I'm not sure why it's not "system".

[DecDuck]

Can you confirm that's the system user? Does it have it's username or anything?