The m_valueSize of VoltType.NULL is -1, so it is not interesting and can be ignored, here -- this is very minor -- I'm not even sure there are ANY case where we serialize NULL type. 

Out of curiosity, it would be interesting to run plannertestrefresh on a branch, commit any change to the baselines, then remove the -1 for VoltType.NULL from the serialization, and then run plannertestrefresh again to look for more changes to the baselines -- just to see if/where we still use VoltType.NULL.