when a deadletterhandler panics grabbit fails to reject the message

[rhinof]

In case the deadletter handler panics grabbit fails to reject the message leaving it permanently in "delivered" state and effectively stops the service

To Reproduce

1. create a bus instance listening to the dlq
2. register a deadletter handler on a dlq bound to a dlx
3. reject a message to the dlx from another service
4. when the deadletter handler is called panic

Expected behavior
The message gets queued back and the handler reprocesses it

Actual behavior
The message remains in the delivered state and the service stops consuming messages from the dlq