“The Green Bird” did not get off to a flying start.A matinee preview on Sunday had to be canceled when actor Reg E. Cathey came into contact with a rapidly moving wall during the performance. Cathey plays Brighella, a soothsayer, in the Julie Taymor-directed fantasy, now at the Cort Theater. Theatergoers were offered a refund or tickets to another performance. Cathey was taken to a hospital for precautionary measures and pronounced to be in excellent condition. He will perform as scheduled today.