@keithm You can fix this on OH 2.2.0 by making sure the “Thermostat read/write v6” permission is enabled in the Nest Developer console.
See: Openhab2 Nest binding - 2.2.0.SNAPSHOT An Updated 2.0 Binding that works!
In OH 2.3.0-SNAPSHOT the binding properly handles missing values due to insufficient permissions.