NEW YORK — An ugly injury to Julius Randle’s right shoulder overshadowed the Knicks’ 125-109 win Saturday over the Miami Heat — and cast doubt about the star forward’s future. Randle crashed to the Madison Square Garden court after his drive to the basket with 4:27 left in the fourth quarter ended with a collision with Miami defender Jaime Jaquez Jr., who tried to draw a charge. The lefty-shooting Randle immediately grabbed his right shoulder and winced before running into the locker room with a trainer. Asked afterward how concerned he was about the injury, Knicks coach Tom Thibodeau replied,…