how did this ever work?

src/ship/location.rs

@@ -146,6 +146,12 @@ impl Default for ClientLocation {
 
 impl ClientLocation {
     pub fn add_client_to_lobby(&mut self, id: ClientId, lobby: LobbyId) -> Result<(), JoinLobbyError> {
+        let l = self.lobbies.get_mut(lobby.0).ok_or(JoinLobbyError::LobbyDoesNotExist)?;
+        if l.0.iter().filter(|c| c.is_none()).count() == 0 {
+            return Err(JoinLobbyError::LobbyFull);
+        }
+        self.remove_client_from_area(id);
+
         let l = self.lobbies.get_mut(lobby.0).ok_or(JoinLobbyError::LobbyDoesNotExist)?;
         let (index, empty_slot) = l.0.iter_mut()
             .enumerate()
@@ -157,7 +163,6 @@ impl ClientLocation {
             local_client: LocalClientId(index),
             time_join: SystemTime::now(),
         });
-        self.remove_client_from_area(id);
         self.client_location.insert(id, RoomLobby::Lobby(lobby));
         Ok(())
     }