Add missing QHash

Summary:
Fixes build with future Frameworks.

In master, this should make 69c492a54b62d380153f2242837ab0433c232e0a obsolete.

Reviewers: alexeymin, KDE Applications, lbeltrame

Reviewed By: alexeymin, KDE Applications, lbeltrame

Differential Revision: https://phabricator.kde.org/D23059