android - from.createForm() は asmack for android の使用中にエラーを生成します

Question

アプリケーションでのチャットに asmack を使用しています。次のコードの実行中にエラーが発生します。

mXmppConnection=connectionToXmppServer(HOST, PORT, SERVICE, mUserName, mPassword);      

/*creating new chat room*/
MultiUserChat muc = new MultiUserChat(mXmppConnection, "DestinationCountry@conference.domainname");

try {

    /*to create chat room*/

    /*sending configration to server*/
      muc.join(mUserName);
     Form form = muc.getConfigurationForm();
      Form answerForm = form.createAnswerForm();

      answerForm.setAnswer("muc#roomconfig_persistentroom", true);

      muc.sendConfigurationForm(answerForm);

    /*muc.sendConfigurationForm(new Form(Form.TYPE_SUBMIT));*/

/*  muc.join("jack");*/

    muc.sendMessage("i just joined the room");
    Log.i("room name", muc.getRoom());
     muc.addMessageListener(new PacketListener() {
            @Override
            public void processPacket(Packet packet) {

                Message mess = (Message) packet;
                Log.i("msg ",mess.getFrom() + ": " + mess.getBody());
            }
        });


} catch (XMPPException e) {

    Toast.makeText(getApplicationContext(), "test room failed",
            Toast.LENGTH_SHORT).show();
}

以下は私が得ているエラーです

02-15 17:54:28.409: E/AndroidRuntime(24400):    at java.lang.Thread.run(Thread.java:856)
02-15 17:54:28.409: E/AndroidRuntime(24400): Caused by: java.lang.NullPointerException
02-15 17:54:28.409: E/AndroidRuntime(24400):    at com.example.groupchat.GroupChat$ConnectTOChatServer.doInBackground(GroupChat.java:174)
02-15 17:54:28.409: E/AndroidRuntime(24400):    at     com.example.groupchat.GroupChat$ConnectTOChatServer.doInBackground(GroupChat.java:1)
02-15 17:54:28.409: E/AndroidRuntime(24400):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
02-15 17:54:28.409: E/AndroidRuntime(24400):    at java.util.concurrent.FutureTask.run(FutureTask.java:234)