ArgumentNullException on trying to mock indexer setter with more than single index argument

[idigra]

See following repro:

int x = default(int);
int y = default(int);
int result = default(int);

var mock = new Mock<IFoo>();
mock.SetupSet(f => f[3, 13] = It.IsAny<int>())
    .Callback(new Action<int, int, int>((x_, y_, result_) =>
              {
                  x = x_;
                  y = y_;
                  result = result_;
              }));

mock.Object[3, 13] = 2;
Assert.Equal(3, x);
Assert.Equal(13, y);
Assert.Equal(2, result);

The issue is a result of the if and explicitly marked with TODO in the code (file src\Moq\Mock.cs):

https://github.com/moq/moq4/blob/22cce9c3f5a7e6a66f079ad719a7e415636430bb/src/Moq/Mock.cs#L670-L677