[BUGFIX] Wrong check removes FE cookie

Issue #55549 added a wrong check for user uid.
As result the FE cookie gets deleted when you are
loggedin instead when your not.

This change inverses the check.

Resolves: #55845
Releases: 6.2
Change-Id: I0c59afb8c89e9f7887970eaf0a4079fe98280b2c
Reviewed-on: https://review.typo3.org/27525
Reviewed-by: Wouter Wolters
Reviewed-by: Markus Klein
Reviewed-by: Marcin Sągol
Reviewed-by: Benjamin Mack
Tested-by: Benjamin Mack