[BUGFIX] Fix PHP 7.2 issues in EXT:lowlevel

Resolves: #83409
Releases: master, 8.7, 7.6
Change-Id: I94a3a3ad31de6e4969d5456f12b728c98adf0815
Reviewed-on: https://review.typo3.org/55206


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>