Randomly switchs to "no wallpaper"

Some times, when I left-click on the tray, or after some time has passed, Drapes shows no wallpaper on the Desktop. I think it's a bug that happens because it tries to switch to a non-existent wallpaper, as I recently removed from the list two wallpapers that I didn't like much.

If that's true, the problem might get worse as changes are made to the display list.