D8309: Modernize: Use nullptr where possible

[Harald Sitter]

sitter accepted this revision.

REPOSITORY
  R871 DrKonqi

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D8309

To: kfunk, sitter, broulik
Cc: broulik, plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, 
jensreuterberg, abetts, sebas, apol, mart