[TASK] Use null coalescing operator where possible

Using null coalescing operator in PHP 7 simplifies code structure.

Resolves: #83129
Releases: master
Change-Id: I449415c99ccb0ea158d3943800bc824514f7629c
Reviewed-on: https://review.typo3.org/54810


Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>