Ignorance is simply a belief in something that is otherwise so. For instance, if I believe this tablecloth is red, when in fact it is yellow, I would be ignorant of its true color. Likewise ignorance is the belief that any object is separate from the absolute self.
Because in reality there are no separate objects, there are no objects. So therefore there cannot be any false knowledge either. For, there cannot be any knowledge of something that does not exist.