create shell surface only at the right moment
Summary:
make the behavior similar to Dialog
create a plasmashell surface only when isVisible() as
some expose events can arrive there too, and also not
create the shell surface if the exposed surface is null
Test Plan: krunner seems to be more reliable
Reviewers: Plasma, davidedmundson
Reviewed By: Plasma, davidedmundson
Subscribers: broulik, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D6299