org-map-entries: Fix org-agenda-prepare-buffers call
* lisp/org.el (org-map-entries): Check that buffer-file-name is non-nil
before passing to org-agenda-prepare-buffers.
Like
11e8749, this surfaced as an error when
05efa7a ("Backport commit
3a5f751 from Emacs master branch", 2015-08-08) replaced a
'(while (setq VAR (pop LIST)) BODY)' with '(dolist (VAR LIST) BODY)',
resulting in the body being executed when '(nil)' was passed to
org-agenda-prepare-buffers.
Reported-by: Robert Klein <roklein@roklein.de>
<http://permalink.gmane.org/gmane.emacs.orgmode/99779>