[BUGFIX] Add default workspace for dummy user

The backend usergroup compare view requires to fetch the
group data of the groups to compare. Since this operation
depends on a user array, UserInformationService creates
such dummy user.

The dummy user array now also contains the default workspace
id `-99` to prevent triggering a database update which would
result in creating a sys log entry. This would fail since the user,
the database update should be performed on, is the dummy
user which is not fully set up.

Resolves: #93233
Releases: master, 10.4
Change-Id: I61870acbab133d9f3f1b80899b50662dca2bc9bf
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/67352

Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>

typo3/sysext/beuser/Classes/Service/UserInformationService.php

@@ -59,8 +59,9 @@ class UserInformationService
         // Setup dummy user to allow fetching all group data
         // @see \TYPO3\CMS\Core\Authentication\BackendUserAuthentication::fetchGroups
         $user->user = [
-            'uid' => 3016,
+            'uid' => PHP_INT_MAX,
             'options' => 3,
+            'workspace_id' => -99,
             $user->usergroup_column => $groupId
         ];
         $user->fetchGroupData();