AirGap material returns absorptance properties even though they aren't defined

Issue overview

AirGap returns absorptance properties even though they aren't defined for the material (https://openstudio-sdk-documentation.s3.amazonaws.com/cpp/OpenStudio-3.2.0-doc/model/html/classopenstudio_1_1model_1_1_air_gap.html).
For example, material.thermalAbsorptance returns 0.0.

Current Behavior

material.thermalAbsorptance, material.solarAbsorptance, material.visibleAbsorptance return 0.0

Expected Behavior

This should raise an undefined method error.

Steps to Reproduce

Using OS CLI:

model = OpenStudio::Model::Model.new
material = OpenStudio::Model::AirGap.new(model)
material.thermalAbsorptance

returns 0.0

Environment

• Windows, openstudio-3.2.0-rc1