D6054: Use explicit flag values or explicit constructor instead of nullptr

[Kevin Funk]

kfunk accepted this revision.
This revision is now accepted and ready to land.

REPOSITORY
  R278 KWindowSystem

BRANCH
  nonullptrforflagsplease

REVISION DETAIL
  https://phabricator.kde.org/D6054

To: kossebau, #plasma, graesslin, kfunk
Cc: plasma-devel, #frameworks, ZrenBot, spstarr, progwolff, lesliezhai, 
ali-mohamed, jensreuterberg, abetts, sebas, apol, mart, lukas