Fix discord bot loading

src/de/steamwar/bungeecore/BungeeCore.java

@@ -172,11 +172,13 @@ public class BungeeCore extends Plugin {
 
     @Override
     public void onDisable(){
+        if (SteamwarDiscordBotConfig.loaded) {
             try {
                 SteamwarDiscordBot.instance().getJda().shutdown();
             } catch (Throwable e) {
                 getLogger().log(Level.SEVERE, "Could not shutdown discord bot", e);
             }
+        }
 
         errorLogger.unregister();
         Statement.closeAll();