Null pointer from deleting non-existent backup

when deleting a CouchbacBackup resource instantly after creating it, operator segfaults.

Reproduction steps:

1. create a cluster with back up enabled
2. apply a backup configuration as per https://docs.couchbase.com/operator/current/howto-backup.html
3. delete the yaml
4. check operator logs for segfault

see attached logs for example