org-refile returns 'invalid target location' when refiling to file root

[Jonathon Anderson <anderbubble@gmail.com>]

org-version 7.7

If I `C-c w` and attempt to refile a tree to the root of a file, the
minibuffer displays "invalid target location" and org-mode fails to
refile the tree.  This works as expected when refiling to a heading
within the same file, or if I have org-refile-use-outline-path set to
`file` rather than `full-file-path`.  (I have idential filenames in
different paths, so I need to use full-file-path.)

I expect this to work because of the documentation for
org-refile-use-outline-path.  Admittedly, this is under the heading of
the `file` value, but I see no reason why it shouldn't be consistent
across the two settings.

> In this case, you can also stop the completion after
> the file name, to get entries inserted as top level in the file.

Do let me know if there's more useful information I can provide.

~jonathon

Applicable `.emacs`:

(setq org-refile-targets
      '(
        (nil :todo . "PROJECT")
        (nil :maxlevel . 1)
        (org-files :maxlevel . 1)
        ))
(setq org-refile-allow-creating-parent-nodes t)
(setq org-refile-use-outline-path 'full-file-path)