[kcmkwin] Make dialog non blocking
Summary:
It's invoked from QML.
Nested event loops invoked directly from QML is asking for crashes.
BUG: 419118
Test Plan:
Opened KCM
Opened dialog for some settings
Window was still modal as before
Settings were saved
(though they didn't seem to be applied..maybe another bug?)
Reviewers: KWin, apol
Reviewed By: apol
Subscribers: zzag, kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D28293