Don’t proxy GetMessages to the leader, fix error handling.
Don’t proxy GetMessages to the leader, fix error handling.

Since https://github.com/Merovius/robustirc/pull/16/files, error
handling was missing, i.e. the client would not get any 404s for invalid
sessions.

robustirc/robustirc,robustirc/robustirc,robustirc/robustirc