Hotfix TablistManager NPE

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

@@ -148,6 +148,9 @@ public class TablistManager extends BasicListener {
         }
 
         private void refresh(){
+            if (player.getServer() == null) {
+                return;
+            }
             ServerInfo currentServer = player.getServer().getInfo();
             setHeader(calcHeader(player));
             // TABLIST_FOOTER=§e{0} {1}§8ms   §eSpieler§8: §7{2}