[XeTeX] accented character ṛ within \section{ṛ}

[Gildas Hamel]

|> I use texlive/2009; TexShop 2.33; and 10.4.11.
|> I am also now using a font called Junicode (http://junicode.sourceforge.net).
|> When the accented character ṛ (-r- with an underdot) is input within
|> \section{}, a box appears in the pdf rather than the character.
|> [....]
|> A minimal example is below.
|> 
|> %!TEX TS-program = xelatex
|> %!TEX encoding = UTF-8 Unicode
|> \documentclass[a4paper,10pt,draft,twoside]{book}
|> \usepackage{xltxtra}
|> \usepackage{lipsum}
|> 
|> \setmainfont[Mapping=tex-text]{Junicode}
|> \defaultfontfeatures{Mapping=tex-text}
|> 
|> \begin{document}
|> \tableofcontents
|> 
|> \chapter{Tṛtīyo 'dhyāyaḥ}
|> Tṛtīyo 'dhyāyaḥ
|> 
|> \lipsum[1-8]
|> 
|> \end{document}


Isn't it possible to use \d{r} in \section{}?
-- gildas