Add missing "}".

Doc/mac/undoc.tex

@@ -85,7 +85,7 @@ available on your machine.
 dialogs and menus, without requiring special case code for when the
 script is run under MacPython, as a MacPython applet or under OSX Python.
 
-\section{\module{Nav --- NavServices calls}
+\section{\module{Nav} --- NavServices calls}
 \declaremodule{standard}{Nac}
   \platform{Mac}
 \modulesynopsis{Interface to Navigation Services}