Well the best I can do is find out who it is attributed to
“Remember that when the chips are down, the buffalo is empty.” -Richard Twiss (Rosebud Lakota/Sioux)
Twiss has wikipedia page
http://en.wikipedia.org/wiki/Richard_Twiss
As to it's meaning, one would have to assume that it has a meaning. It might just be a funny saying.
Sayings don't always have to have a meaning.