Upsert/Insert null with MutateIn fails with Invalid arguments (0x0004)

        [Fact]

        public async Task Upsert_and_remove_when_inserting()

        {

            var collection = await _fixture.GetDefaultCollection().ConfigureAwait(false);

            var documentKey = nameof(Upsert_and_remove_when_inserting) + Guid.NewGuid().ToString();

            var sampleDoc = new {foo = "bar"};

            var insertResult =

                await collection.InsertAsync(documentKey, sampleDoc, opts => opts.Expiry(TimeSpan.FromSeconds(30)));

            ////var mutateInResult = await collection.MutateInAsync(documentKey, specs =>

            ////    specs.Upsert("xattr1", string.Empty, isXattr: true, createPath: true)

            ////        .Remove("xattr1", isXattr: true)

            ////        .SetDoc(sampleDoc));

            ///

            var result = await collection.MutateInAsync(documentKey, specs =>

                specs.Insert("bar", (object)null));

        }