fix: only set runningGame to true if the client actually had a started game

Server/src/main/java/uulm/teamname/marvelous/server/lobbymanager/LobbyManager.java

@@ -42,7 +42,10 @@ public class LobbyManager {
      */
     public boolean handleConnect(Client client, AtomicBoolean running) {
         if (participants.containsKey(client.getId())) {
-            running.set(true);
+            LobbyConnection lobby = lobbies.get(participants.get(client.getId()).lobby);
+            if (lobby != null) {
+                running.set(lobby.state == LobbyConnectionState.Started);
+            }
         }
         return true;
     }