997 Airbag light stays on after battery discharged.

My battery tender became disconnected and my battery totally discharged. I am given to understand that if current goes to zero, the air bag light remains on. Do I have to now pay to have the code cleared ( $150) or purchase a code reader and reset. Perhaps you could recommend one that is appropriate ? Or, can I just disconnect the battery completely and will that remove the code and reset the airbag light so it doesn’t stay on ? Thank you.