error when class has list as property and list is null

[parfilko]

error when class has list as property and list is null.
here is example:

Declare classes:

    public class ZZZ
    {
        public string aaa { get; set; } = "zzz aaa";
        public string bbb { get; set; } = "zzz bbb";
    }
    public class YYY
    {
        public List<ZZZ> zzz;              //   field !!!
        public string aaa { get; set; } = "yyy aaa";
        public string bbb { get; set; } = "yyy bbb";
    }
    public class XXX
    {
        public List<ZZZ> zzz { set; get; }  //  property !!!
        public string aaa { get; set; } = "xxx aaa";
        public string bbb { get; set; } = "xxx bbb";
    }

code:

    var zzList = new List<ZZZ>() { new ZZZ(), new ZZZ(), new ZZZ() };           //  some list

    var yy = new List<YYY>() {
            new YYY() { zzz = zzList },
            new YYY() { zzz = zzList }
    };
            
    var xx = new List<XXX>() {
            new XXX() { zzz = zzList },
            new XXX() { zzz = zzList }
    };
            
    var lstYY = new BindingListView<YYY>(yy);   //  ok
    var lstXX = new BindingListView<XXX>(xx);   //  ok

    // recreate with zzz = null
    yy = new List<YYY>() {
            new YYY(),
            new YYY()
    };

    xx = new List<XXX>() {
            new XXX(),
            new XXX()
    };

    lstYY = new BindingListView<YYY>(yy);       //  ok
    lstXX = new BindingListView<XXX>(xx);       //  error

`