gsmi: fix null-deref in gsmigetvariable
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 v4.19.271 by commit 32313c11bdc8a02c577abaf865be3664ab30410a, it was introduced in version v3.0 by commit 74c5b31c6618f01079212332b2e5f6c42f2d6307. For more details please see the references link.