Jennifer Lopez shows off her toned abs in stomach-baring shirt as she celebrates with American Idol's Top 13

By SARAH BULL Tanned and toned: Jennifer Lopez shows off her impressive toned stomach as she arrives at the American Idol finalists party last nightShe might be 41 and the mother of two-year-old twins, but Jennifer Lopez proved last night she still has the body of a 20-year-old as she attended the American Idol finalists party in a stomach-baring shirt and tiny shorts.The singer smiled and waved