Also need to guard the period

Co-authored-by: Henrik Tidefelt <henrikt@wolfram.com>

chapters/packages.tex

@@ -388,7 +388,7 @@ \section{Multilingual Descriptions}\label{multilingual-descriptions}
 
 At first there can be an optional comment describing the location (file name and line number) of the text to translate. Multiple occurences of the same string can be listed here, separated by space.
 
-Then, the \lstinline!<context identifier>! behind the keyword \lstinline!msgctxt! is the full name of the Modelica class (e.g. \lstinline!Modelica.Blocks.Math.Sin!) where the text appears in.
+Then, the \lstinline!<context identifier>! behind the keyword \lstinline!msgctxt! is the full name of the Modelica class (e.g., \lstinline!Modelica.Blocks.Math.Sin!) where the text appears in.
 Short class definitions do not appear here.
 Texts in such classes belong to the enclosing full class definition.