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

[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