Timeboxed for investigation: 3 SP, double-check the updated app as well; impact on SPA in old pages app

Reproduction steps:

1. Go to https://demo.magnolia-cms.com/.magnolia/admincentral
2. Unhide the old pages app by deleting `/modules/ui-admincentral/config/appLauncherLayout/hiddenApps@pages`
3. Log out and back in
4. Go to old pages app
5. Edit page /sportstation
6. Add new component to 'main' area
7. Add Image and Text component
8. With just an image
9. Save changes on the dialog
10. Observe component is not visible
11. Refresh page
12. Component is visible
13. Delete component
14. Observer component is still visible
15. Refresh page
16. Observe component gone