RFC2616 says in section 5.1.2:
Note that the absolute path cannot be empty; if none is present in the original URI, it MUST be given as "/"
Furthermore, I don't think that absolute URLs are valid in HTTP/1.0 unless it is a proxy request?
So this is really an issue with the client and or proxy that you are using. What is the client? Also what jetty version and connector are you using?
However, I'm not opposed to looking at adding an option to automatically convert empty path to /. But as we've never had complaints before, I'd like to know a bit more about the use-case before we make such a change.