The first cub born to female lion Nababiep (pictured) earlier this week has died. Photo by Mehgan Murphy, courtesy Smithsonian’s National Zoo. Awful news for baby animal lovers. Officials at the Smithsonian’s National Zoo confirm that the lion cub born Tuesday has died. Lion keepers observed Thursday evening that the cub had stopped responding to its mother, and after moving mom Nababiep out of her den, were able to confirm the death. The cub…