net, neigh: Fix null-ptr-deref in neightableclear()
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 v5.10.154 by commit 1c89642e7f2b7ecc9635610653f5c2f0276c0051, it was introduced in version v5.10.141 by commit c35adafe42bd6c3bf2aca0a3f523dabc38fc23c8. For more details please see the references link.