fix: discord disconnect message broken (blame VoiceChatPlugin! not discord's fault!)

src/main/java/me/chayapak1/chomens_bot/Bot.java

@@ -41,7 +41,7 @@ import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
 public class Bot extends SessionAdapter {
-    private final ArrayList<Listener> listeners = new ArrayList<>();
+    private final List<Listener> listeners = new ArrayList<>();
 
     public final String host;
     public final int port;

src/main/java/me/chayapak1/chomens_bot/plugins/VoiceChatPlugin.java

@@ -206,7 +206,7 @@ public class VoiceChatPlugin extends Bot.Listener implements Runnable {
 
     @Override
     public void disconnected (final DisconnectedEvent event) {
-        socket.close();
+        if (socket != null) socket.close();
         groups.clear();
 
         running = false;