Knicks fans thwarted the Philadelphia 76ers’ evil plot to block them from Game 4 of the play-offs at Xfinity Mobile Arena in Philly on Sunday — packing the site to watch their beloved team cruise to victory. “It’s terrible,” admitted Sixers fan Tiffany Fenstermaker of Allentown, Pa., to The Post during halftime at the arena. “The whole stadium is Knicks fans!” Knicks diehard Kehos Herz of Brooklyn brings a broom to the Philly arena to manifest a Knicks sweep of the 76ers — and it works! Aristide Economopoulos for NY Post A security guard at the stadium estimated that the crowd was “about 90 percent” for the Knicks. “All you can see is blue and orange,” he said. The overwhelming New York representation occurred after Sixers’ star Joel Embiid last week urged Philadelphia-area ticket-holders not to sell to New York fans.…