libiptc: minor bugfix

Minor bugfix, an extra check is needed if the tail element is a
builtin chain, as builtin chains are not sorted.

Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: Patrick McHardy <kaber@trash.net>
diff --git a/libiptc/libiptc.c b/libiptc/libiptc.c
index d0f51b4..ec5317b 100644
--- a/libiptc/libiptc.c
+++ b/libiptc/libiptc.c
@@ -819,7 +819,8 @@
 		list_add_tail(&c->list, &h->chains);
 	else {
 		ctail = list_entry(tail, struct chain_head, list);
-		if (strcmp(c->name, ctail->name) > 0)
+		if (strcmp(c->name, ctail->name) > 0 ||
+		    iptcc_is_builtin(ctail))
 			list_add_tail(&c->list, &h->chains);/* Already sorted*/
 		else
 			iptc_insert_chain(h, c);/* Was not sorted */