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 v4.9.318 by commit 50c341f9a2adc4c32a8ad5a39eb99d9c4a419e0d. For more details please see the references link.