Bug :: Mapping of Decimal to JS type (4.0.2)

An ObjC error leaks into the JS evaluation space if we evaluate the well-formed expression:

    x => x.totalCost

Cannot convert "0", type 13 to an NSAppleEventDescriptor

This is a fairly minor error for most practical purposes, as x.totalCost.toString() works fine, but it does suggest some misalignment of types, or a leaky wrapper, at that point.