Greeter calls wallpaper twice time at the same login screeen.

Although user chose the wallpaper, Greeter doesn't show it at the first time.
Only shows default purple wallpaper during login, but, moving session by up and down key to choose one.
It seems greeter calls wallpaper twice time in the same login screen.
First calls the default purple wallpaper right after first boot up,
and secondarily ,while moving cursor, call the user configured wallpaper.

It means also that it is the same case if users use default purple wallpaper.
then greeter already displayed wallpaper twice time while users are not conginzed it.
right after boot up first showing default wallpaper, while moving cursor second wallpaper is displayed.