[ticket/12518] Apply De Morgan to make the conditions easier to read

PHPBB3-12518
Merge pull request #2446 from nickvergessen/ticket/12518

[ticket/12518] Apply De Morgan to make the conditions easier reasable

* nickvergessen/ticket/12518:
  [ticket/12518] Apply De Morgan to make the conditions easier to read
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12518] Apply De Morgan to make the conditions easier to read