save the containment only aftyer switch
Summary:
during a type switch
if the new containment gets saved before getting a view,
it will get lastScreen=-1 so the next boot
it will create a new containment
Test Plan:
switched repeatedly between desktop and folderview
the config file always got with the correct lastScreen=0 entry
Reviewers: Plasma
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D2966