Fix TablistManager

src/de/steamwar/bungeecore/listeners/TablistManager.java

@@ -50,7 +50,9 @@ public class TablistManager extends BasicListener {
     @EventHandler
     public synchronized void onJoin(PostLoginEvent e){
         BungeeCord.getInstance().getScheduler().schedule(BungeeCore.get(), () -> {
-            tablists.put(e.getPlayer(), new Tablist(e.getPlayer()));
+            if (BungeeCord.getInstance().getPlayer(e.getPlayer().getUniqueId()) != null) {
+                tablists.put(e.getPlayer(), new Tablist(e.getPlayer()));
+            }
         }, 1, TimeUnit.SECONDS);
     }