iouring: Fix a null-ptr-deref in iotctxexitcb()
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 v5.15.83 by commit f895511de9d27fff71dad2c234ad53b4afd2b06c, it was introduced in version v5.12 by commit d56d938b4bef3e1421a42023cdcd6e13c1f50831. For more details please see the references link.