protobuf-net：处理IEnumerable中的空值？通过什么属性/设置？

Some sample code below. The interesting/problem case is the Data property in Mad. This code blows up (null value in the enumerable). Also, it works if i don't use the static attributes but instead the runtime type model, where i put in member.SupportNull = true for the fields (which is the behaviour i want), so what am i missing in the attributes / settings? Google search seems to indicate this is an open issue with probuf-net? That the same functionality is not available via attributes?Some sample code below. The interesting/problem