tty: fix possible null-ptr-defer in spkttyiorelease
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 v5.15.90 by commit 2da67bff29ab49caafb0766e8b8383b735ff796f, it was introduced in version v5.12 by commit 4f2a81f3a88217e7340b2cab5c0a5ebd0112514c. For more details please see the references link.