Fix GHNS bug when we add a cursor theme you can't delete it or choose cursor size
Test Plan: Install a theme through GHNS, and check if you can delete it / change cursor size (if available for this theme)
Reviewers: Plasma, ervin, meven, crossi
Subscribers: apol, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D26051