tracing: Fix potential double free in createvarref()
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 v4.19.247 by commit f8b383f83cb573152c577eca1ef101e89995b72a, it was introduced in version v4.17 by commit 067fe038e70f6e64960d26a79c4df5f1413d0f13. For more details please see the references link.