[BUGFIX] Remove dead-code paths from AddController

PHPStan identified these code paths as impossible. On
code inspection that's true, so they have been removed
as dead code.  That allowed for the properties of the
class to be typed.

Small related cleanup is included to make verifying
that the code paths were indeed dead easier.

Resolves: #97621
Releases: main
Change-Id: Icc5e53ef72fedb9fc5de659b22229d61c8502f1e
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/74636


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>