NullpointerException please help me i could not make it work.

package com.ahmetyuva.ribbit;

import android.app.AlertDialog;
import android.app.ListActivity;
import android.support.v4.app.NavUtils;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.parse.FindCallback;
import com.parse.ParseException;
import com.parse.ParseQuery;
import com.parse.ParseRelation;
import com.parse.ParseUser;

import java.util.List;


public class RecipientsActivity extends ListActivity{

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

    protected List<ParseUser> mFriends;
    protected ParseRelation<ParseUser> mFriendsRelation;
    protected ParseUser mCurrentUser;

    protected MenuItem mSendMenuItem;

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

        getActionBar().setDisplayHomeAsUpEnabled(true);

        getListView().setChoiceMode(ListView.CHOICE_MODE_MULTIPLE);
    }

    @Override
    public void onResume() {
        super.onResume();

        mCurrentUser = ParseUser.getCurrentUser();
        mFriendsRelation = mCurrentUser.getRelation(ParseConstants.KEY_FRIENDS_RELATION);

        ParseQuery<ParseUser> query = mFriendsRelation.getQuery();
        query.addAscendingOrder(ParseConstants.KEY_USERNAME);
        query.findInBackground(new FindCallback<ParseUser>() {
            @Override
            public void done(List<ParseUser> friends, ParseException e) {

                if(e == null) {

                    mFriends = friends;

                    String[] usernames = new String[mFriends.size()];
                    int i = 0;
                    for (ParseUser user : mFriends) {
                        usernames[i] = user.getUsername();
                        i++;

                    }                   ArrayAdapter<String> adapter = new ArrayAdapter<String>(
                            getListView().getContext(),
                            android.R.layout.simple_list_item_checked,
                            usernames);
                    setListAdapter(adapter);
                }
                else{

                    Log.e(TAG, e.getMessage());
                    AlertDialog.Builder builder = new AlertDialog.Builder(RecipientsActivity.this);
                    builder.setMessage(e.getMessage())
                            .setTitle(R.string.error_title)
                            .setPositiveButton(android.R.string.ok, null);

                    AlertDialog dialog = builder.create();
                    dialog.show();

                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_recipients, menu);
        mSendMenuItem = menu.getItem(0);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        switch (item.getItemId()){
            case android.R.id.home:

                NavUtils.navigateUpFromSameTask(this);
                return true;
            case R.id.action_send:
                return true;
        }
      /*  int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
*/
        return super.onOptionsItemSelected(item);
    }

    @Override
    protected void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

        if (l.getCheckedItemCount() > 0) {
            mSendMenuItem.setVisible(true);
        } else {
            mSendMenuItem.setVisible(false);
        }
    }
}