mod_invites_adhoc: Set non-nil defaults for options, fixes traceback (thanks Martin) Fixes an error when attempting to call the :empty() method on the default implicit default nil value.

2c07bcf56a36d6e74dc0f5422e89bd61f4d31239 0.8-diverge
1656d4fd71d07aa3a52da89d4daf7723a555e7dd last-google-code-commit