[BUGFIX] Category localization cannot be rendered

Localized sys_category records cannot be rendered in frontend,
since only records with a positive pid value are overlaid -
however, sys_category is stored on the root-level.

Resolves: #56059
Releases: 6.2, 6.1
Change-Id: I211dad5086adf30723ef4f44757fe6a3121ac29e
Reviewed-on: https://review.typo3.org/27673
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader