D9399: Fix crash, presumably since Qt 5.10?

[David Faure]

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

REPOSITORY
  R241 KIO

BRANCH
  master

REVISION DETAIL
  https://phabricator.kde.org/D9399

To: apol, #frameworks, dfaure
Cc: anthonyfieroni, ngraham