Display Default Image from Generic Handler when no image in database in ASP.NET

Handler.ashx file code :

public class ImageHandler : IHttpHandler
    {

        public void ProcessRequest(HttpContext context)
        {
            Int32 theID;
            if (context.Request.QueryString["AdminId"] != null)
                theID = Convert.ToInt32(context.Request.QueryString["AdminId"]);
            else
                throw new ArgumentException("No parameter specified");

            context.Response.ContentType = "image/jpeg";
            Stream strm = DisplayImage(theID);
            byte[] buffer = new byte[2048];
            int byteSeq = strm.Read(buffer, 0, 2048);

            while (byteSeq > 0)
            {
                context.Response.OutputStream.Write(buffer, 0, byteSeq);
                byteSeq = strm.Read(buffer, 0, 2048);
            }
        }

        public Stream DisplayImage(int theID)
        {
            SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString.ToString());
            string sql = "SELECT Image FROM Admins WHERE AdminId = @AdminId";
            SqlCommand cmd = new SqlCommand(sql, connection);
            cmd.CommandType = CommandType.Text;
            cmd.Parameters.AddWithValue("@AdminId", theID);
            connection.Open();
            object theImg = cmd.ExecuteScalar();
            try
            {
                return new MemoryStream((byte[])theImg);
            }
            catch
            {
                return null;
            }
            finally
            {
                connection.Close();
            }
        }

        public bool IsReusable
        {
            get
            {
                return false;
            }
        }
    }

If Image record null in database then i want to set default image in return value , So how can do it