bug#19916: 24.4; rmail-summary-next-msg declares argument incorrectly

[schule@fsavigny.de (Florian v. Savigny)]

As I am fairly certain that this is a bug in the source code, I am not including any of the automatic information on my system which M-x report-emacs-bug produces.

Description of the bug:  rmail-summary-next-msg declares its attribute
	       	   	 NUMBER as &optional, but does not treat it
	       	   	 like that, at least when called
	       	   	 non-interactively.

Reproducible: always

How: Calling (rmail-summary-next-msg) non-interactively.

Undesired behaviour:

	  Throws the following exception:

	  	 and: Wrong type argument: number-or-marker-p, nil

	  This is an obscure error if you have called
	  (rmail-summary-next-message) in accordance with the
	  documentation.

Explanation:	This can easily be tracked to the following line in the source
		code for the function, where it expects NUMBER to be non-nil:

		(and (> number 0) (end-of-line)) ;; line 3 after the docstring

Line 827 in the source file in the following version of rmailsum.el:
;; Copyright (C) 1985, 1993-1996, 2000-2014 Free Software Foundation,


Workaround: Calling (rmail-summary-next-msg 1) instead of using no argument.




Best regards,

Florian v. Savigny