[XeTeX] Dotless I and Emph problem

[Chris Yocum]

Hi Everyone,
     I was in the process of moving my thesis over from PDFTeX to
XeTeX when I noticed a peculiar problem.  When you have a dotless i in
an emph command, it becomes un-italic.  I am not sure if this is a
Linux Libertine problem (the font that I am using) or a XeTeX problem
so I thought that I would start here first.  Below is a minimal
example.

Thanks in advance and for all the hard work on XeTeX,
Chris

\documentclass{article}

\usepackage{xunicode}
\usepackage{xltxtra}
\usepackage{fontspec}
\setmainfont[Mapping=tex-text]{Linux Libertine O}

\begin{document}

F\'{\i}thal

\emph{F\'{\i}thal}

\end{document}