Fix error in reading config

Created by: eseliger

Closes #7866

This is a fix for the root cause of the noise reported in #7866 When reading a config value here: { action: ACTION_ID, when: 'get(config.experimentalFeatures, "searchStats")' }, the parser did not account for experimentalFeatures being not an object (here null). For properties on objects that don't exist, we return undefined instead now and the errors are gone