Tomcat 5.5.12 and user-agent header

[Richard Mixon]

I tested out my application on 5.5.12 yesterday and noticed one small
anomally. I had a JSP in my sitemesh decorator "default.jsp" that ends up
wrapping the login page for container managed authentication. This page had
a statement
    String  _userAgent = request.getHeader("user-agent").toLowerCase();
 
It gets a null-pointer exception in 5.5.12, but under 5.5.9 it runs fine. In
5.5.12, after the login succeeds then the user-agent headers appear to be
there just fine, but not on the initial login page.
 
Is this a known issue?
 
Thank you - Richard