ContainmentItem: set correct constraints when wallpaper is ready
Not all wallpaper plugins set their loading status to keep the splash screen on, which means if the current wallpaper plugin is ready, there is no isLoadingChanged signal, so the ui constraints will never be updated. This adds a check to fix it.
BUG: 482267 FIXED-IN: 6.0.2
Edited by Fushan Wen