applets/kicker: fix crash when current activity changes
Reason for the change
In Private's ctor, a ResultSet will query the current activity which might cause Kickoff to preload its full representation, which will refresh the root model and eventually call KAStatsFavoritesModel::refresh, which leads to a crash because d-ptr is not ready yet.
Test plan
Screenshots or screen recordings
Bugs fixed
SENTRY: PLASMA-WORKSPACE-125Z FIXED-IN: 6.2.1