Unlikely. If nothing else fortified places provide a fallback in the case your field army gets manhandled, so the only cities without walls would be those that for some reason think they don't need them (Sparta?), can't afford them, or are actively forbidden by someone with the authority from having them. And I don't really see why the Muslim princes (who were pretty soon squabbling with each other anyway) would not have walls around their cities for defensive purposes.