yet another attempt at fixing ability to join non-existent lobbies

lobby.js

@@ -42,8 +42,7 @@ app.get("/lobby/join", async (req, res) => {
     if (!user) {
         return res.status(401).json({error: "User doesn't exist"});
     }
-    for (let lobby of playerMap) {
-        if (playerMap[lobby.lobbyId] == lobbyId) {
+    if (playerMap[lobbyId]) {
         await joinLobby(lobbyId, user.username);
 
         if (!playerMap[lobbyId]) {
@@ -56,7 +55,6 @@ app.get("/lobby/join", async (req, res) => {
 
         res.json({lobbyId, username});
     } else console.log("Lobby with " + lobbyId + " not found.");
-    }
 });
 
 app.get("/lobby/players", async (req, res) => {