can anyone see why I'm getting a Null Pointer exception on exit
<p>Here is a short List activity that calls a custom adapter to show class room attendance.
I set up the data using the classroom rowid that was clicked to get here and then query my
DB to get all students in the class. I use a custom adapter because I have a list of checkboxes
along with student names. No matter if I use my adapter or simply substitute in simplecursoradapter (and lose my checkbox functionality) upon exit I get a null pointer exception. This happens whether
I click the "done" button or click the back arrow. I can't seem to see anything.  Can you?</p>

<pre><code>public class ShowStudentAttendance extends ListActivity {
private gradeBookDbAdapter mDbHelper;
private Long mRowId;
private TextView mNameText;
private String classname;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    Cursor stud;

    mDbHelper = new gradeBookDbAdapter(this);
    mDbHelper.open();
    mRowId = (savedInstanceState == null) ? null
            : (Long) savedInstanceState
                    .getSerializable(gradeBookDbAdapter.KEY_ROWID);
    if (mRowId == null) {
        Bundle extras = getIntent().getExtras();
        mRowId = extras != null ? extras
                .getLong(gradeBookDbAdapter.KEY_ROWID) : null;
    }
    if (mRowId != null) {
        stud = mDbHelper.fetchClass(mRowId);
        startManagingCursor(stud);

        classname = stud.getString(
                stud.getColumnIndexOrThrow(gradeBookDbAdapter.KEY_CLASSNAME));
        String title = "Attendance for " + classname;
        setTitle(title);
    }
    stud = mDbHelper.fetchAllStudentsClass(mRowId);
    startManagingCursor(stud);
    setContentView(R.layout.attendance_list);
    Button doneButton = (Button) findViewById(R.id.Done);
    doneButton.setOnClickListener(mAttendanceActivity);


    // Create an array to specify the fields we want to display in the list (only name)
    String[] from = new String[]{gradeBookDbAdapter.KEY_NAME,
            gradeBookDbAdapter.KEY_ROWID};

    // and an array of the fields we want to bind those fields to (in this case just text1)
    int[] to = new int[]{R.id.stuname};

    // Now create a simple cursor adapter and set it to display
    MyDataAdapter studs = 
       new MyDataAdapter(this, R.layout.show_attendance, stud, from, to);
    setListAdapter(studs);
}
private OnClickListener mAttendanceActivity = new OnClickListener() {
    public void onClick(View v) {
        setResult(RESULT_OK);
        finish();
    }

};

}
</code></pre>
