lua: fix inverted argument check in ubus_lua_add

The guard 'if (lua_istable(L, 1))' was backwards: it raised an error
when argument 1 IS a table, but argument 1 is always the ubus_context
userdata (never a table). The intent was to reject calls where argument
2 is NOT a table.

As a result, any call to ubus.add(c, non_table) silently proceeded to
lua_next() on a non-table value, causing a crash, while a valid call
with a proper table as argument 2 was never incorrectly rejected only
because arg 1 never matches lua_istable.

Fix by checking !lua_istable(L, 2).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Link: https://github.com/openwrt/ubus/pull/20
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

1 files changed, 1 insertions, 1 deletions

diff --git a/lua/ubus.c b/lua/ubus.c
index 07b816d..47dd837 100644
--- a/lua/ubus.c
+++ b/lua/ubus.c
@@ -559,7 +559,7 @@ static int ubus_lua_add(lua_State *L)
 	struct ubus_lua_connection *c = luaL_checkudata(L, 1, METANAME);
 
 	/* verify top level object */
-	if (lua_istable(L, 1)) {
+	if (!lua_istable(L, 2)) {
 		lua_pushstring(L, "you need to pass a table");
 		return lua_error(L);
 	}