Leere listView

public class MyAdapter extends SimpleCursorAdapter {

private Cursor cursor;
private LayoutInflater inflater;

private int columnIndexRowID;
private int columnIndexFromAddrString;
private int columnIndexToAddrString;

public LastRequestsAdapter(Context context, int layout, Cursor c,
        String[] from, int[] to) {
    super(context, layout, c, from, to);
    this.cursor = c;
    this.inflater = LayoutInflater.from(context);

    this.columnIndexRowID = c.getColumnIndex(MyDBAdapter.KEY_ROWID);
    this.columnIndexFromAddrString = c
            .getColumnIndex(MyDBAdapter.KEY_FROM_ADDR_STRING);
    this.columnIndexToAddrString = c
            .getColumnIndex(MyDBAdapter.KEY_TO_ADDR_STRING);

}
@Override
public View getView(int position, View convertView, ViewGroup parent) {

    ViewHolder viewHolder;

    if(convertView==null){

        convertView = this.inflater.inflate(R.layout.main_activity_last_request_row, null);
        viewHolder = new ViewHolder();
        viewHolder.id = -1;
        viewHolder.fromAddr = (TextView) convertView.findViewById(R.id.from);
        viewHolder.toAddr =(TextView) convertView.findViewById(R.id.to);
        viewHolder.arrow = (ImageView) convertView.findViewById(R.id.last_request_arrow);
        convertView.setTag(viewHolder);
    }else {
        viewHolder = (ViewHolder) convertView.getTag();
    }

    this.cursor.moveToPosition(position);

    viewHolder.id = this.cursor.getInt(columnIndexRowID);
    viewHolder.fromAddr.setText(this.cursor.getString(this.columnIndexFromAddrString));
    viewHolder.toAddr.setText(this.cursor.getString(this.columnIndexToAddrString));
    viewHolder.arrow.setImageResource(R.drawable.arrow_alt);

    return convertView;

}

public class ViewHolder{
    public int id;
    public TextView fromAddr;
    public TextView toAddr;
    public ImageView arrow;
 }
}

listView.setAdapter(new MyAdapter(this,
            R.layout.main_activity_last_request_row, dbCursor,
            new String[] { MyDBAdapter.KEY_FROM_ADDR_STRING,
                    MyDBAdapter.KEY_TO_ADDR_STRING }, new int[] {
                    R.id.from, R.id.to }));

(convertView == null)