updateDisplay() null object reference

    public static final String TAG = MainActivity.class.getSimpleName();

    private CurrentWeather mCurrentWeather;

    @BindView(R.id.timeLabel) TextView mTimeLabel;
    @BindView(R.id.tempLabel) TextView mTemperatureLabel;
    @BindView(R.id.humidValue) TextView mHumidityValue;
    @BindView(R.id.precipValue) TextView mPrecipValue;
    @BindView(R.id.summaryLabel) TextView mSummaryLabel;
    @BindView(R.id.iconImageView) ImageView mIconImageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

       ButterKnife.bind(this);

        String apiKey = "****************************************";
        double latitude = 37.8267;
        double longitude = -122.423;
        String forecastURL = "https://api.forecast.io/forecast/" + apiKey +
                "/" + latitude + "," + longitude;
        if(isNetworkAvailable()) {
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    .url(forecastURL)
                    .build();

            Call call = client.newCall(request);
            call.enqueue(new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {

                }

                @Override
                public void onResponse(Call call, Response response) throws IOException {
                    try {
                        String jsonData =  response.body().string();
                        Log.v(TAG, jsonData);
                        if (response.isSuccessful()) {
                            mCurrentWeather = getCurrentDetails(jsonData);
                            runOnUiThread(new Runnable() {
                                @Override
                                public void run() {
                                    updateDisplay();
                                }
                            });
                        } else {
                            alertUserAboutError();
                        }
                    } catch (IOException | JSONException e) {
                        Log.e(TAG, "Exception caught: ", e);
                    }
                }
            });
        }
        else {
            Toast.makeText(this, R.string.toast_conn_msg, Toast.LENGTH_LONG).show();
        }
    }

    private void updateDisplay() {
        mTemperatureLabel.setText(mCurrentWeather.getTemp() + "");
        mTimeLabel.setText("At " + mCurrentWeather.getFormattedTime() + "it will be");
        mHumidityValue.setText(mCurrentWeather.getHumidity() + "");
        mPrecipValue.setText(mCurrentWeather.getPrecipChance() + "%");
        mSummaryLabel.setText(mCurrentWeather.getSummary());

    }

    private CurrentWeather getCurrentDetails(String jsonData) throws JSONException {
        JSONObject forecast = new JSONObject(jsonData);
        String timezone = forecast.getString("timezone");
        Log.i(TAG, "From JSON: " + timezone);

        JSONObject currently = forecast.getJSONObject("currently");

        CurrentWeather currentWeather = new CurrentWeather();
        currentWeather.setHumidity(currently.getDouble("humidity"));
        currentWeather.setTime(currently.getLong("time"));
        currentWeather.setIcon(currently.getString("icon"));
        currentWeather.setPrecipChance(currently.getDouble("precipProbability"));
        currentWeather.setSummary(currently.getString("summary"));
        currentWeather.setTemp(currently.getDouble("temperature"));
        currentWeather.setTimeZone(timezone);


        Log.d(TAG, currentWeather.getFormattedTime());

        return currentWeather;
    }


    private boolean isNetworkAvailable() {
        ConnectivityManager manager = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = manager.getActiveNetworkInfo();
        boolean isAvailable = false;
        if(networkInfo != null && networkInfo.isConnected()) {
            isAvailable = true;
        }
        return isAvailable;
    }

    private void alertUserAboutError() {
        AlertDialogueFragment dialog = new AlertDialogueFragment();
        dialog.show(getFragmentManager(), "error_dialog");
    }
}