Why does the App crash if I use it without Internet?

You see, I have an App with a Bottom bar with 5 buttons corresponding to 5 fragments, and when entering the application, of course, it loads the first fragment which is a database. The code of said fragment is the following:

public class First_fragment extends Fragment {

    ListView lstCursos;
    String recuperado;
    public final static String CLAVE_EXTRA_PASAR2 = "true";

    private ListView mylist;

    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View v = inflater.inflate(R.layout.first_tab, container, false);
        //De este modo cambiamos el tema para cada uno de los layout
        getActivity().setTheme(R.style.Barra);

        getActivity().setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

        Bundle recupera = getActivity().getIntent().getExtras ();
        if (recupera != null) {
            recuperado = recupera.getString ( "cod" );
        }

        Thread tr2 = new Thread () {
            @Override
            public void run() {
                final String resultado = enviarGET ( recuperado ); //LINEA 55
                getActivity().runOnUiThread ( new Runnable () {
                    @Override
                    public void run() {
                        ////////////////////////////////////////
                        cargarListView ( ArregloLista ( resultado ) );
                        ////////////////////////////////////////
                    }
                } );
            }
        };
        tr2.start ();
        return v;
    }

    public String enviarGET(String id){

        URL url = null;
        String linea = "";
        int respuesta = 0;
        StringBuilder resul = null;

        try {
            //url = new URL ("http://192.168.1.41/WebService/llenarnoticias.php?id="+id);
            url = new URL ("http://rudeboys.esy.es/ramiroconnect/llenarnoticias.php?id="+id);
            //Ahora enviamos el dato
            HttpURLConnection conection = (HttpURLConnection) url.openConnection ();
            //Guardamos la respuesta en el entero, porque sera un uno o un cero
            //Esto es lo que devuelve la BD una vez hacemos la consulta
            respuesta = conection.getResponseCode ();
            //Inicializamos resul
            resul = new StringBuilder ();

            if (respuesta == HttpURLConnection.HTTP_OK) {
                InputStream in = new BufferedInputStream(conection.getInputStream());
                BufferedReader reader = new BufferedReader (new InputStreamReader(in));

                while ((linea = reader.readLine ()) != null){
                    resul.append (linea);
                }
            }
        } catch (Exception e) {
            Intent intencion = new Intent(getActivity(),Federaciones.class);
            intencion.putExtra(CLAVE_EXTRA_PASAR2, "true");
            startActivity(intencion);
        }
        return resul.toString (); // LINEA 101
    }

    //Metodo que permite crear un arraylista para llena el listview
    public ArrayList<String> ArregloLista(String response){
        ArrayList<String> listado = new ArrayList<String> ();
        try {
            JSONArray json = new JSONArray (response);
            String texto = "";
            String texto2 = "";
            for(int i=0;i<json.length ();i++){
                texto = json.getJSONObject(i).getString("titulo");
                texto2 = json.getJSONObject(i).getString("descripcion");
                listado.add("\n" + texto + "\n\n" +texto2 + "\n");
            }
        } catch (Exception e) {}
        return listado;
    }

    //Aquí es donde va TODA LA CHICHA
    public void cargarListView(ArrayList<String> datos){
        ArrayAdapter<String> adaptador = new ArrayAdapter<String> (getActivity(), android.R.layout.simple_list_item_1, datos);
        lstCursos = (ListView) getActivity().findViewById (R.id.listCursos);
        lstCursos.setAdapter (adaptador);
    }
}

Lo que sucede que si la uso sin Wi-Fi o sin datos, es decir, sin Internet, la App crashea al iniciarla, supongo que será porque como no hay Internet no puede accedes a la data base. Por tanto intenté poner en el **Main Activity un try-catch donde llamo al 1º fragment para que no crasheara sin éxito alguno** : 



``if (i == R.id.one) {``  // AQUI CARGO EL PRIMER FRAGMENT

                    First_fragment f1 = new First_fragment();
                    getSupportFragmentManager().beginTransaction().replace(R.id.frame, f1).commit();
                    currentFragment  = 1;
                }

                if (i == R.id.two) { // AQUI CARGO EL SEGUNDO FRAGMENT

                    //Second_fragment f2 = new Second_fragment();
                    Second_renovado_fragment f2 = new Second_renovado_fragment();
                    getSupportFragmentManager().beginTransaction().replace(R.id.frame, f2).commit();
                    currentFragment  = 2;
                }

                if (i == R.id.three) { AQUI CARGO EL TERCER FRAGMENT

                    Three_fragment f3 = new Three_fragment();
                    getSupportFragmentManager().beginTransaction().replace(R.id.frame, f3).commit();
                    currentFragment  = 3;
                }

                if (i == R.id.four) { // AQUI CARGO EL CUARTO FRAGMENT

                    Four_fragment_list f4 = new Four_fragment_list();
                    getSupportFragmentManager().beginTransaction().replace(R.id.frame, f4).commit();
                    currentFragment  = 4;
                }

                if (i == R.id.five) {  // AQUI CARGO EL QUINTO FRAGMENT
                    Map_fragment f5 = new Map_fragment();
                    getSupportFragmentManager().beginTransaction().replace(R.id.frame, f5).commit();
                   // startActivity(new Intent(MainActivity1.this, MapActivity.class));
                    currentFragment  = 5;
                }
            }

        });

        mBottomBar.mapColorForTab(0, "#c92029");
        mBottomBar.mapColorForTab(1, "#c92029");
        mBottomBar.mapColorForTab(2, "#c92029");
        mBottomBar.mapColorForTab(3, "#c92029");
        mBottomBar.mapColorForTab(4, "#c92029");

        // seems this is  working to highlist tab
        mBottomBar.selectTabAtPosition(0, true);



        try {  ////////ESTE ES EL TRY-CATCH DEL QUE HABLO//////////

            // Loading first Fragment to FrameLayout manually
            First_fragment f1 = new First_fragment();
            getSupportFragmentManager().beginTransaction().replace(R.id.frame, f1).commit();
        }catch (Exception e){}

What I can do ?

What appears in the log:

01-24 11:30:01.345 18876-18981/com.test.rudeboys.rudeboys1 E/AndroidRuntime: FATAL EXCEPTION: Thread-4172 java.lang.NullPointerException at com.test.rudeboys.rudeboys1.First_fragment.sendGET(First_fragment.java :101) at com.test.rudeboys.rudeboys1.First_fragment$1.run(First_fragment.java:55)

I have commented lines 55 and 101 that give errors in the log in the above code to easily locate them