customer.subscription.deleted webhook event not working (should it be?)

I have webhooks configured for these events:

invoice.payment_succeeded
invoice.payment_failed
charge.failed
charge.refunded
charge.succeeded
charge.captured
customer.subscription.updated
customer.subscription.deleted

I have noticed that in particular the "customer.subscription.deleted" one does not work, because the api call on line 497 of CRM/Core/Payment/StripeIPN.php fails with "Expected one contribution, found 0" due to $this->charge_id being empty.

Is this a bug or are some webhook events just not implemented in the extension & should not be configured? Is there a list somewhere of which webhook events are supported? thank you!