[SCSI] zfcp: prevent fc_remote_port_delete calls for unregistered rport

In case of an adapter reopen all rports have to be deleted from the
environment. This should only happen for already registered rports
otherwise fc_remote_port_delete is called with a NULL pointer.
Signed-off-by: NSwen Schillig <swen@vnet.ibm.com>
Signed-off-by: NChristof Schmitt <christof.schmitt@de.ibm.com>
Signed-off-by: NJames Bottomley <James.Bottomley@HansenPartnership.com>

drivers/s390/scsi/zfcp_erp.c

@@ -1236,6 +1236,8 @@ static void zfcp_erp_rports_del(struct zfcp_adapter *adapter)
 {
 	struct zfcp_port *port;
 	list_for_each_entry(port, &adapter->port_list_head, list) {
+		if (!port->rport)
+			continue;
 		fc_remote_port_delete(port->rport);
 		port->rport = NULL;
 	}