nilfs2: fix NULL pointer dereference at nilfsbmaplookupatlevel()
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.15.74 by commit 1e512c65b4adcdbdf7aead052f2162b079cc7f55. For more details please see the references link.