NullRefrenceException was unhandled by user code
Code below is placed in page_Load. How I should handle this to bypass UrlReferrel when you enter page directly first time and there is no referrer? 
What I am missing here?

        if (HttpContext.Current.Request.UrlReferrer.AbsoluteUri != null)
        {
            urlReferer = HttpContext.Current.Request.UrlReferrer.AbsoluteUri.ToString();
        }
        else
        {
            urlReferer = "";
        }
NullRefrenceException was unhandled by user code
===

Code below is placed in page_Load. How I should handle this to bypass UrlReferrel when you enter page directly first time and there is no referrer? 
What I am missing here?

        if (HttpContext.Current.Request.UrlReferrer.AbsoluteUri != null)
        {
            urlReferer = HttpContext.Current.Request.UrlReferrer.AbsoluteUri.ToString();
        }
        else
        {
            urlReferer = "";
        }