fix gcc warnings

Max Kellermann <max@duempel.org>
diff --git a/extensions/libxt_iprange.c b/extensions/libxt_iprange.c
index 47d7464..51b35f8 100644
--- a/extensions/libxt_iprange.c
+++ b/extensions/libxt_iprange.c
@@ -27,7 +27,7 @@
 static const struct option iprange_mt_opts[] = {
 	{.name = "src-range", .has_arg = true, .val = '1'},
 	{.name = "dst-range", .has_arg = true, .val = '2'},
-	{},
+	{ .name = NULL }
 };
 
 static void