Background slider hides slides if you delete one image from media library

Hey there.

My client added new pictures and deleted the older ones on the media library, but he didn't deleted them from the background slider. Now he cannot add any more images as the sliders area is drawn empty. I think there's an error as the files do not exists, and that stops the rendering of that area. I don't have access to the server so I have not been able to see the error log. but once I get it, I will let you know.