Give this daredevil an asterisk. High-wire artist Nik Wallenda became the first man to brave certain doom by walking over the rushing water of Niagara Falls on a tightrope last night. The American acrobat successfully made the crossing on a 2-inch-thick wire in 25 minutes — but the stunt wasn’t as death defying as it seemed. Wallenda, 33, was forced to wear a safety harness by ABC, which broadcast the event. ,