Fix crash in ShellContainmentModel::load and improve panels and desktop management preview
requested to merge tcosprojects/plasma-workspace:471292-fix-crash-containment-fix-preview into Plasma/5.27
This merge request includes two commits:
- Fix a use-after-free crash in ShellContainmentModel::load.
- Correct a bug in the panels and desktop management preview behavior. The bug was not previously noticeable due to the aforementioned crash.
If these should be split into separate merge requests, please let me know.