During command registration, grub_register_command_prio() returns
a 0 when there is a failure in memory allocation. In such a situation,
calls to grub_unregister_{command(), extcmd()} during command
unregistration will result in dereferencing a NULL pointer.
Perform explicit NULL check in both unregister helpers to prevent
undefined behaviour due to a NULL pointer dereference.
Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
Reviewed-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
fa93f2412b