Calls to starget_to_rport() may return NULL.  Add check for NULL rport
before dereference.

Link: https://lore.kernel.org/r/20220603174329.63777-5-jsmart2021@gmail.com
Fixes: bb21fc99 ("scsi: lpfc: Use fc_block_rport()")
Cc: <stable@vger.kernel.org> # v5.18
Co-developed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>