Dereferencing a Null 2D Array Row

What is the result when the following code is executed?

public class NullRow {
    public static void main(String[] args) {
        int[][] arr = new int[2][];
        arr[0] = new int[]{1, 2};
        arr[1] = null;
        System.out.println(arr[1].length);
    }
}