doInBackground throws NullPointerException for no reason

In here the code with BufferedReaderand line = reader.readLine() works

public class WeatherService extends AsyncTask<TaskParams, Void, String> {
private WeatherServiceCallback callback;
private Exception exception;

public WeatherService(WeatherServiceCallback callback) {
    this.callback = callback;
}

@Override
protected String doInBackground(TaskParams... params) {
    try {
        URL url = new URL("http://api.openweathermap.org/data/2.5/weather?lat=" +
                params[0].getLat() + "&lon=" + params[0].getLon() +
                "&units=" + TaskParams.getUnits() +
                "&type=" + TaskParams.getAccuracy() + "&lang=" + TaskParams.getLanguage() +
                "&appid=10660a09a9fb335d72f576f7aa1bbe5b");

        URLConnection connection = url.openConnection();
        InputStream inputStream = connection.getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
        StringBuilder builder = new StringBuilder();
        String line;

        while ((line = reader.readLine()) != null) {
            builder.append(line);
        }

        return builder.toString();
    } catch (MalformedURLException e) {
        exception = e;
    } catch (IOException e) {
        exception = e;
    }

    return null;
}

@Override
protected void onPostExecute(String s)
{
    if (s == null && exception != null)
    {
        callback.serviceFailure(exception);
        return;
    }

    try
    {
        JSONObject data = new JSONObject(s);
        Parameters parameters = new Parameters();
        parameters.poopulate(data);
        callback.serviceSuccess(parameters);
    } catch (JSONException e) {
        e.printStackTrace();
    }
}
}

I copy-pasted code to other class since it has very similar functionality and now for no reason I'm getting NullPointerException in while ((line = reader.readLine()) != null) and I have no idea why since as I said it's copy-pasted (I only changed URL and object returned if serivce succeeds)

public class PollutionService extends AsyncTask<TaskParams, Void, String>
{

private PollutionServiceCallback callback;
private Exception exception;
private URLConnection connection;
private InputStream inputStream;
private InputStreamReader streamReader;
private BufferedReader reader;

public PollutionService(PollutionServiceCallback callback) {
    this.callback = callback;
}

@Override
protected String doInBackground(TaskParams... params) {
    try
    {
        URL url = new URL("http://api.openweathermap.org/pollution/v1/co/" + params[0].getLat() +
                "," + params[0].getLon() + "/current.json?&appid=10660a09a9fb335d72f576f7aa1bbe5b");

        try
        {
            connection = url.openConnection();
        }

        catch (IOException e)
        {
            exception = new Exception("Connection error");
        }

        try
        {
            inputStream = connection.getInputStream();
        }

        catch (IOException e)
        {
            exception = new Exception("Input stream error");
        }

        try
        {
            streamReader = new InputStreamReader(inputStream);
        }

        catch (NullPointerException e)
        {
            exception = new Exception("Input stream reader error");
        }

        try
        {
            reader = new BufferedReader(streamReader);
        }

        catch (NullPointerException e)
        {
            exception = new Exception("Buffered reader error");
        }

        StringBuilder builder = new StringBuilder();
        String line;

        try
        {
            while ((line = reader.readLine()) != null)
            {
                builder.append(line);
            }
        }

        catch (IOException e)
        {
            exception = e;
        }

        return builder.toString();
    }
    catch (MalformedURLException e)
    {
        exception = e;
    }

    return null;
}

@Override
protected void onPostExecute(String s)
{
    if (s == null && exception != null)
    {
        callback.pollutionServiceFailure(exception);
        return;
    }

    try
    {
        JSONObject data = new JSONObject(s);
        PollutionParameters parameters = new PollutionParameters();
        parameters.poopulate(data);
        callback.pollutionServiceSuccess(parameters);
    } catch (JSONException e) {
        e.printStackTrace();
    }
}
}

Any clue?