fix bad sync against no messages for mockroom

secert-hitler/src/controller/gamemaster/gamemaster.rs

@@ -82,6 +82,10 @@ mod tests {
       let room_id = r1.room_id();
       let mut gm = GameMaster::new(r1);
       let mut r2 = mrs.join(room_id).unwrap();
+      r2.send(r#"{
+         "msgtype": "m.text",
+         "body": ""
+      }"#);
       gm.run_lobby();
       assert!(gm.lobby.players.len() == 1, "players: {:?}, sync: {:?}", gm.lobby.players, gm.room.sync());
    }