syntax and error in ncf log

[mary sarami]

How would I code the below so that if session is null, it produces no errors.
The below doesn't produce an error but in the ncf error log it give a null 500 servlet error. but the page is fine.
Thanks
<%
String refURL = request.getHeader("referer");
out.println (refURL);
if (refURL !=null)
//if (session !=null)
if (refURL.endsWith("one.jsp") ) {
out.println("one.jsp");
%>
<jsp:forward page="one.jsp"/>

<%
} else {
out.println("seesion is null");
<% } %>