fix gcc warnings

Max Kellermann <max@duempel.org>
diff --git a/extensions/libxt_TOS.c b/extensions/libxt_TOS.c
index 74ec2b5..777d7cf 100644
--- a/extensions/libxt_TOS.c
+++ b/extensions/libxt_TOS.c
@@ -20,7 +20,7 @@
 
 static const struct option tos_tg_opts_v0[] = {
 	{.name = "set-tos", .has_arg = true, .val = '='},
-	{},
+	{ .name = NULL }
 };
 
 static const struct option tos_tg_opts[] = {
@@ -28,7 +28,7 @@
 	{.name = "and-tos", .has_arg = true, .val = '&'},
 	{.name = "or-tos",  .has_arg = true, .val = '|'},
 	{.name = "xor-tos", .has_arg = true, .val = '^'},
-	{},
+	{ .name = NULL }
 };
 
 static void tos_tg_help_v0(void)