tty: synclinkgt: Fix null-pointer-dereference in slgtclean()
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 v4.14.283 by commit 078212ad15dbd88840c82c97f12c93d83703c8fd. For more details please see the references link.