Update get_param() description to reflect changes to the docstring.
diff --git a/Doc/lib/emailmessage.tex b/Doc/lib/emailmessage.tex
index f580edf..372c539 100644
--- a/Doc/lib/emailmessage.tex
+++ b/Doc/lib/emailmessage.tex
@@ -354,15 +354,18 @@
Parameter keys are always compared case insensitively. The return
value can either be a string, or a 3-tuple if the parameter was
\rfc{2231} encoded. When it's a 3-tuple, the elements of the value are of
-the form \code{(CHARSET, LANGUAGE, VALUE)}, where \code{LANGUAGE} may
-be the empty string. Your application should be prepared to deal with
-3-tuple return values, which it can convert to a Unicode string like
-so:
+the form \code{(CHARSET, LANGUAGE, VALUE)}. Note that both \code{CHARSET} and
+\code{LANGUAGE} can be \code{None}, in which case you should consider
+\code{VALUE} to be encoded in the \code{us-ascii} charset. You can
+usually ignore \code{LANGUAGE}.
+
+Your application should be prepared to deal with 3-tuple return
+values, and can convert the parameter to a Unicode string like so:
\begin{verbatim}
param = msg.get_param('foo')
if isinstance(param, tuple):
- param = unicode(param[2], param[0])
+ param = unicode(param[2], param[0] or 'us-ascii')
\end{verbatim}
In any case, the parameter value (either the returned string, or the