gh-54732: Make argparse error caused by empty rows in option files explicit

Doc/library/argparse.rst

@@ -440,6 +440,12 @@ were in the same place as the original file referencing argument on the command
 line.  So in the example above, the expression ``['-f', 'foo', '@args.txt']``
 is considered equivalent to the expression ``['-f', 'foo', '-f', 'bar']``.
 
+.. note::
+
+   Empty lines are treated as empty strings (''), which are allowed as values but not
+   as arguments. Empty lines as arguments will result in an “unrecognized arguments” 
+   error.
+
 :class:`ArgumentParser` uses :term:`filesystem encoding and error handler`
 to read the file containing arguments.