GSD-2022-1002399 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 v4.14.276 by commit 33bd243566a9b1ca94261dcc2e16c7b9e3a71c15...