org.eclipse.jetty.ee9.nested.Request method returning `null`

**Jetty version(s)** Jetty 12.1.4

**Jetty Environment** ee9

**Description**

Various functions of the `org.eclipse.jetty.ee9.nested` class, for example [`getRequestURI()`](https://github.com/jetty/jetty.project/blob/jetty-12.1.x/jetty-ee9/jetty-ee9-nested/src/main/java/org/eclipse/jetty/ee9/nested/Request.java#L1276), are allowed to return `null`. This contrasts with the interface description of the method (https://jakarta.ee/specifications/servlet/5.0/apidocs/jakarta/servlet/http/httpservletrequest#getRequestURI()), and it makes debugging a very erratic process.

My questions:
1. What is the reason for the variant behavior?
2. I cannot find hints to the current design choices in the Java sources. Is the Jetty-specific behavior documented somewhere?
3. Unchecked exceptions would not be ideal either, but they could at least give some more hints on what is going on. Have you thought about that?

Start with jetty-ee9/jetty-ee9-nested/src/main/java/org/eclipse/jetty/ee9/nested/Request.java, especially getRequestURI(), and compare its behavior with the Jakarta Servlet 5.0 HttpServletRequest description. Review the issue's three questions and Jetty 12.1.4 ee9 behavior; done means the null-returning behavior and any intended documentation or change are clearly resolved.

Written by the indexing model from the issue text.