provide a NullAnalyticsParser if no analytics provider is given
provide a NullAnalyticsParser if no analytics provider is given

this dynamic `include` strategy seems like it could be approved upon with a more
conventional dependency injecton or Strategy pattern approach. in the meanwhile,
don't `NameError` on startup if no analytics provider is specified.

samvera/hyrax,samvera/hyrax,samvera/hyrax,samvera/hyrax