Auto-unboxing need of ternary if-else

This piece of code works fine :-

    if (1 <= 3) {
        Integer secondNull = nullInt;
    } else {
        Integer secondNull = -1;
    }
    System.out.println("done");

But this throws null-pointer exception, while Eclipse warning that there is need for auto-unboxing :-

    Integer nullInt = null;
    Integer secondNull = 1 <= 3 ? nullInt : -1;
    System.out.println("done");

Why is that so, can somebody guide please?