Twitter4J + Android: Authentication Challenge is Null Exception

I'm using Twitter4J library for OAuth authentication but I get "Authentication Challenge is Null Exception" even before It opens the Twitter login page.

Here is the code.

    Twitter twitter = new TwitterFactory().getInstance();
    try
    {

        twitter.setOAuthConsumer(Startup.TWITTER_KEY, Startup.TWITTER_SECRET);

        String callbackURL = "twitter-client:///";

        RequestToken rToken = twitter.getOAuthRequestToken(callbackURL);

        startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(rToken.getAuthenticationURL())));

    }
    catch(IllegalStateException e)
    {
    // access token is already available, or consumer key/secret is not set.
        if(!twitter.getAuthorization().isEnabled()){
            System.out.println("OAuth consumer key/secret is not set.");
            System.exit(-1);
        }
    }
    catch(Exception e)
    {
        Toast.makeText(Home.this, "Network Host not responding: "+e.getMessage(),Toast.LENGTH_SHORT).show();  //This exception. 
    }

Exception:

E/Home ( 4393): Received authentication challenge is null E/Home ( 4393): Received authentication challenge is nullRelevant discussions can be on the Internet at: E/Home ( 4393): http://www.google.co.jp/search?q=6c607809 or E/Home ( 4393): http://www.google.co.jp/search?q=0f1d8134 E/Home ( 4393): TwitterException{exceptionCode=[6c607809-0f1d8134 cab4c0ac-d492a113], statusCode=-1, retryAfter=0, rateLimitStatus=null, version=2.2.2} E/Home ( 4393): at twitter4j.internal.http.HttpClientImpl.request(HttpClientImpl.java:204) E/Home ( 4393): at twitter4j.internal.http.HttpClientWrapper.request(HttpClientWrapper.java:65) E/Home ( 4393): at twitter4j.internal.http.HttpClientWrapper.post(HttpCl