During his concert last night at the The Troubadour in Los Angeles, Harry Styles was joined on stage by Stevie Nicks. The two sang Styles’ recent single “Two Ghosts” as well as the Fleetwood Mac classic, “Landslide” and Nicks’ “Leather and Lace.” As Pitchfork notes, at one point during the performance, Styles—who says he once gave Nicks…