spotted by Marcin Gołębski

proposed fix:

                if(is != null && os != null)
                {
                    int count = 0;
                    while(count >= 0)
                    {
                        count = is.read(buffer, 0, buffer.length);
                        if(count > 0)
                        {
                            os.write(buffer, 0, count);
                        }
                    }
                    os.flush(); // <-- os.close() here
                }