GSD-2022-1001695 jfs: prevent NULL deref in diFree

jfs: prevent NULL deref in diFree 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 v5.15.34 by commit d925b7e78b62805fcc5440d1521181c82b6f03cb. F...