Bug: Recursive publish with :base-extension any fails [9.1.1 (9.1.1-1-g80cbf9-elpaplus @ /Users/xxxx/.emacs.d/elpa/org-plus-contrib-20170918/)]

[Keith Sutton <kesutt@gmail.com>]

When org-publish-project-alist has both :base-extension any and
:recursive t set, the publish fails with "(wrong-type-argument stringp
nil)" in a call to string-match in directory-files-recursively.

It looks like org-publish-get-base-files should set match to "" rather
than nil when :base-extension is any. In my minimal testing this works
fine for me, but I'll leave it to the experts to figure out if that
would negatively affect other things.

Org mode version 9.1.1 (9.1.1-1-g80cbf9-elpaplus @
/Users/xxxx/.emacs.d/elpa/org-plus-contrib-20170918/)

(I have two projects: one to publish the org files to HTML, and one
for everything else that doesn't meet some exclusion criteria. There
may or may not be a better way to do this, but the combination of
:base-extension any, :recursive t, and an :exclude regexp was the
first thing to come to mind.)

-- 
Keith Sutton