Implicit operator problem

implicitboom.cs

    internal class Bla
    {
        public int Blaat { get; }

        public Bla(int blaat) => Blaat = blaat;

        public static implicit operator int(Bla x) => x.Blaat;
    }

    internal class Bleh
    {
        public Bla Bla { get; }

        public Bleh(Bla bla) => Bla = bla;
    }

    internal class Program
    {
         private static void Main(string[] args)
        {
            var a = new Bleh(new Bla(42));
            int? aa = a.Bla;

            var b = new Bleh(null);
            int? bb = b.Bla; // This explodes because it calls the implicit operator, but the inner value is null

            return;
        }
    }