안드로이드 - 서버에서json받기-listview출력 - org.json.JSONException에러 ㅠㅠ

class BackgroundTask extends AsyncTask<Void, Void, String> {
        String target;
        JSONObject jsonObject;
        JSONArray jsonArray;
 
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            try {
                target = "http://sanghoboy135.cafe24.com/courseList.php?courseUniversity=" + URLEncoder.encode(courseUniversity, "UTF-8") +
                        "&courseYear=" + URLEncoder.encode(yearSpinner.getSelectedItem().toString().substring(0, 4), "UTF-8") + "&courseTerm=" + URLEncoder.encode(termSpinner.getSelectedItem().toString(), "UTF-8") +
                        "&courseArea=" + URLEncoder.encode(areaSpinner.getSelectedItem().toString(), "UTF-8") + "&courseMajor=" + URLEncoder.encode(majorSpinner.getSelectedItem().toString(), "UTF-8");
                //문제1
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
 
        @Override
        protected String doInBackground(Void... voids) {
            try {
                URL url = new URL(target);
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
                if (connection != null) {
                    connection.setRequestMethod("GET");
                    connection.getResponseCode();
                }
                InputStream inputStream = connection.getInputStream();
                BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
                String temp;
                StringBuilder builder = new StringBuilder();
                while ((temp = reader.readLine()) != null) {
                    builder.append(temp + "\n");
                }
                reader.close();
                inputStream.close();
                connection.disconnect();
                return builder.toString().trim();
            } catch (Exception e) {
                e.printStackTrace();
            }
            return null;
        }
 
        @Override
        protected void onProgressUpdate(Void... values) {
            super.onProgressUpdate(values);
        }
 
        @Override
        protected void onPostExecute(String s) {
            super.onPostExecute(s);
 
            Log.d("냐옹", s);
            try {
 
                JSONObject jsonObject = new JSONObject(s);
                JSONArray jsonArray = jsonObject.getJSONArray("response");
 
                int count = 0;
 
                int courseID;
                String courseUniversity;
                int courseYear;
                String courseTerm;
                String courseArea;
                String courseMajor;
                String courseGrade;
                String courseTitle;
                int courseCredit;
                int courseDivide;
                int coursePersonnel;
                String courseProfessor;
                String courseTime;
                String courseRoom;
 
                courseList = new ArrayList<Course>();
 
                    while (count < jsonArray.length()) {
                        JSONObject object = jsonArray.getJSONObject(count);
 
                        courseID = object.getInt("courseID");
                        courseUniversity = object.getString("courseUniversity");
                        courseYear = object.getInt("courseYear");
                        courseTerm = object.getString("courseTerm");
                        courseArea = object.getString("courseArea");
                        courseMajor = object.getString("courseMajor");
                        courseGrade = object.getString("courseGrade");
                        courseTitle = object.getString("courseTitle");
                        courseCredit = object.getInt("courseCredit");
                        courseDivide = object.getInt("courseDivide");
                        coursePersonnel = object.getInt("coursePersonnel");
                        courseProfessor = object.getString("courseProfessor");
                        courseTime = object.getString("courseTime");
                        courseRoom = object.getString("courseRoom");
                        Log.d("냐옹", "고양이");
                        Log.d("냐옹", courseUniversity);
                        Course course = new Course(courseID, courseUniversity, courseYear, courseTerm, courseArea, courseMajor, courseGrade, courseTitle, courseCredit, courseDivide, coursePersonnel, courseProfessor, courseTime, courseRoom);
                        courseList.add(course);
 
 
                        count++;
                    }
 
 
 
 
                //Course course = new Course(1, "학부", 2016, "1학기", "교양및기타", "군사학", "3", "군사학", 2, 1, 0, "허진회", "", "");
 
                //courseList.add(course);
                adapter = new CourseAdapter(getActivity(), courseList);
                courseListView.setAdapter(adapter);
                /*if(count == 0){
                    AlertDialog.Builder dialog = new AlertDialog.Builder(getActivity());
                    dialog.setMessage("조회된 강의가 없습니다.")
                            .setPositiveButton("확인", null)
                            .create();
                    dialog.show();
                }
                */
                //adapter.notifyDataSetChanged();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

서버에서 데이터받아온 후 리스트뷰에 출력하려고 합니다. 그런데 postExecute부분에서 자꾸

W/System.err: org.json.JSONException: Value null of type org.json.JSONObject$1 cannot be converted to JSONObject 이런 에러가 뜹니다. 구글링 해봤는데 exception때문인것같아 여러가지 해봤는데도 안되네요. 데이터는 제대로 불러오고 있습니다. 다만 출력이 안됩니다. 도와주세용 ㅠㅠ