GSD-2022-1002186 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 v5.4.189 by commit e19c3149a80e4fc8df298d6546640e01601f3758. F...