[ticket/12437] Clean up redundant "clear" elements & "corners"

PHPBB3-12437
Merge remote-tracking branch 'PayBas/ticket/12437' into develop-ascraeus

* PayBas/ticket/12437:
  [ticket/12437] Clean up redundant "clear" elements & "corners"
Merge branch 'develop-ascraeus' into develop

* develop-ascraeus:
  [ticket/12437] Clean up redundant "clear" elements & "corners"