drm/radeon: fix a possible null pointer dereference
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 v5.4.198 by commit 28fd384c78d7d8ed8af0d086d778c3e438ba7f60. For more details please see the references link.