Fix crash in KCMKeyboardWidget::populateWithCurrentXkbOptions on Wayland
Summary:
Prevents a call into X11 which will crash. This needs to be fixed
properly by defining a way to get the options from the Wayland
compositor.
Test Plan: Can open the KCM without crash
Reviewers: Plasma
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D6581