JsonSyntaxException: java.lang.IllegalStateException: Expected an int but was BOOLEAN

public ArrayList<MoodleCourse> getEnrolledCourses(String userId) {
    ArrayList<MoodleCourse> mCourses = new ArrayList<MoodleCourse>();
    String format = MoodleRestOption.RESPONSE_FORMAT;
    String function = MoodleRestOption.FUNCTION_GET_ENROLLED_COURSES;

    try {
        // Adding all parameters.
        String params = "&" + URLEncoder.encode("userid", "UTF-8") + "="
                + userId;

        // Build a REST call url to make a call.
        String restUrl = mUrl + "/webservice/rest/server.php" + "?wstoken="
                + token + "&wsfunction=" + function
                + "&moodlewsrestformat=" + format;

        /
        MoodleRestCall mrc = new MoodleRestCall();
        Reader reader = mrc.fetchContent(restUrl, params);
        GsonExclude ex = new GsonExclude();
        Gson gson = new GsonBuilder()
                .addDeserializationExclusionStrategy(ex)
                .addSerializationExclusionStrategy(ex).create();
        mCourses = gson.fromJson(reader,
                new TypeToken<List<MoodleCourse>>() {
                }.getType());
        reader.close();

    } catch (Exception e) {
        Log.d(DEBUG_TAG, "URL encoding failed");
        e.printStackTrace();
    }

    return mCourses;
}