if it's already defined just leave it, only put the missing codes and files, and modify what needs to be modified especially on the public.xml and smali parts.. you have to understand what the codes do, don't just follow every detail on a guide, use your logic. to make it easier though use an unmodified systemui and follow the guide to every detail but if you're modifying an already modified apk you have to figure it out yourself as it would be slightly or completely different.
owh you mean just ignore that error and continues to editing public.xml? ok i will try..