The linguistic concept of meaning implies the concept of the linguistic referent. In other words, the meaning of a sign is a characterization of its referent. The meaning is a relation of the sign to its referent. These include Case and agreement. This cannot be the case.
All morphemes have referents and, consequently, meaning.
The distinction between direct and indirect reference does not make sense. Yes, case and agreement, as well as gender, have meaning. The meaning of grammatical is abstract, but there is no morpheme without a meaning. In the course of the history of a language some morphemes may lose their meaning, and then they are no more morphemes. This analysis is wrong.