I have 3 source items to map to a destination. There is a possibility the third item will be null. I create a config as follows: ``` var config = TypeAdapterConfig<(a, b, c), Output>.NewConfig() .Map(dest => dest, src => src.Item1) .Map(dest => dest, src => src.Item2) .Map(dest => dest.Application, src => src.Item3 == null ? (Application) null : new Application() { Id = src.Item3.Id, Name = src.Item3.Name }) ``` My expectation was that a null value for Item3 should be handled and a null value returned for the Application property of the output. When I run the mapping: ` var result = (x, y, z)Adapt<Output>(config.Config); ` when z is null, then a NullReferenceException is thrown. Is this a bug?