Null pointer dereference

In the Linux kernel, the following vulnerability has been resolved:

nvme-fc: Prevent null pointer dereference in nvme_fc_io_getuuid()

The nvme_fc_fcp_op structure describing an AEN operation is initialized with a
null request structure pointer. An FC LLDD may make a call to
nvme_fc_io_getuuid passing a pointer to an nvmefc_fcp_req for an AEN operation.

Add validation of the request structure pointer before dereference.