D19732: [KWidgetAddons] Fix build with Qt 5.13

[Aleix Pol Gonzalez]

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

REPOSITORY
  R236 KWidgetsAddons

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D19732

To: matthieugras, apol
Cc: kde-frameworks-devel, michaelh, ngraham, bruns