Moved polyglossia/babel definitions to before biblatex; otherwise biblatex fails with xetex.

default.latex

@@ -49,6 +49,15 @@ $endif$
 $if(geometry)$
 \usepackage[$for(geometry)$$geometry$$sep$,$endfor$]{geometry}
 $endif$
+$if(lang)$
+\ifxetex
+  \usepackage{polyglossia}
+  \setdefaultlanguage{$lang$}
+  \setmainlanguage{$mainlang$}
+\else
+  \usepackage[$lang$]{babel}
+\fi
+$endif$
 $if(natbib)$
 \usepackage{natbib}
 \bibliographystyle{$if(biblio-style)$$biblio-style$$else$plainnat$endif$}
@@ -123,14 +132,6 @@ $endif$
 $if(verbatim-in-note)$
 \VerbatimFootnotes % allows verbatim text in footnotes
 $endif$
-$if(lang)$
-\ifxetex
-  \usepackage{polyglossia}
-  \setmainlanguage{$mainlang$}
-\else
-  \usepackage[$lang$]{babel}
-\fi
-$endif$
 
 $if(title)$
 \title{$title$$if(subtitle)$\\\vspace{0.5em}{\large $subtitle$}$endif$}