isdn: icn: NULL dereference printing error message

"card2" is NULL here so I have changed it to use "id2" instead of
"card2->interface.id".
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/isdn/icn/icn.c

@@ -1580,8 +1580,7 @@ icn_addcard(int port, char *id1, char *id2)
 	}
 	if (!(card2 = icn_initcard(port, id2))) {
 		printk(KERN_INFO
-		       "icn: (%s) half ICN-4B, port 0x%x added\n",
-		       card2->interface.id, port);
+		       "icn: (%s) half ICN-4B, port 0x%x added\n", id2, port);
 		return 0;
 	}
 	card->doubleS0 = 1;