Keith Urban is the man in the middle. The new “American Idol” judge had to play peacemaker between Nicki Minaj and Mariah Carey. Video leaked to TMZ shows Minaj and Carey in a heated and profane argument. Urban says he feels like the United Nations. He made the comment on the red carpet Wednesday at the New York Film Festival gala honoring his wife, Nicole Kidman. “Idol” debuts in January.