Store stashed model index as QPersistentModelIndex
Summary:
Otherwise we can crash if the model updates during load.
CCBUG: 390005
CCBUG: 385557
Test Plan:
Had a state where my manually saved session would crash systemsettings on load
accessing a null kservice object from a menuItem
With this patch that session no longer crashes
Reviewers: Plasma, apol
Reviewed By: apol
Subscribers: apol, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D24785