Condition value of "null" is treated in a peculiar and inconsistent way by condition expander

The condition transformer is hard-coded to apply a special meaning to the value "null" when seen as a condition value. In its implementation is
if (condition === null)

{ return undefined; }

There seems to be no reason to retain this branch and it should be removed. It's worth noting that the condition expander differs subtly from some others as well - in that a value of "undefined" for the condition is also interpreted. It has become a general standard that a transformer becomes entirely inactivated by being supplied values which are all "undefined". Certainly, if every input to the condition transformer is undefined, this remains the case - but we should start working harder to ensure there is a consistent idiom for these cases across all transformers, and write down a standard that applies to them.