如下代码在注释行会报错，原因是：getSeatTravelerInfo()时值为空，对空对象addAll会报错

SeatBookingInfo b=new SeatBookingInfo();

b.setIndex(index);

b.setContactInfo(contactInfo);

// b.getSeatTravelerInfo().addAll(seatTravelerInfo);

b.setSeatTravelerInfo(seatTravelerInfo);

addAll()报NullPointer原因