core: Length of undefined is 0. It's fine. Quiet some errors.

src/util.js.c

@@ -401,6 +401,11 @@ void tf_util_register(JSContext* context)
 
 int tf_util_get_length(JSContext* context, JSValue value)
 {
+	if (JS_IsUndefined(value))
+	{
+		return 0;
+	}
+
 	JSValue length = JS_GetPropertyStr(context, value, "length");
 	int result = 0;
 	JS_ToInt32(context, &result, length);