desktoppackage/ConfigurationAppletPage: handle non-loaded item
ConfigurationAppletPage takes the Loader height from the loaded item. This can be computed before the loader is ready, at which point the item is null and does not have the required properties yet, causing a TypeError.
Instead use optional chaining to avoid the error.
Test plan:
- Right-click desktop, "Desktop and Wallpaper"
- (without) lots of errors (with) still lots of errors, but not that one particular TypeError.