Heidi Klum had a postvacation glow as she strode onto the set of The Tonight Show With Jay Leno yesterday. The supermodel, who wore a sexy corset dress for the appearance, has spent most of the Summer traveling with Seal and their children. Heidi flaunted a rotating wardrobe of two-pieces during their many afternoons on the beaches of Italy and Spain, but she told Jay she would rather don only bikini bottoms. Heidi prefers going topless, she revealed, because she can't stand tan lines. The typically candid Project Runway host saw the latest season of the show she helped create kick off last month, and this Fall, a spin-off series called Project Runway All Stars will air on Lifetime, as well.