[BUGFIX] Do not use self:: within closures

This is not possible in PHP 5.3.

Resolves: #59203
Releases: 6.2
Change-Id: I108578f7635c50493a3b5d7a7fc81c021805abf8
Reviewed-on: https://review.typo3.org/30489
Reviewed-by: Markus Klein
Tested-by: Markus Klein