[O] [bug?] Actions grouped by priority

[Sebastien Vauban]

Hello,

With the following snippet, I'd expect to see *all* actions in one (and
just one) of the following lists:

- with priority #A
- with priority #B
- with priority #C
- with no priority

--8<---------------cut here---------------start------------->8---
    (add-to-list 'org-agenda-custom-commands
                 '("p" "Actions Grouped by Priority"
                   ((tags-todo "+PRIORITY={A}")
                    (tags-todo "+PRIORITY={B}")
                    (tags-todo "+PRIORITY={C}")
                    (tags-todo "+PRIORITY={}"))))
--8<---------------cut here---------------end--------------->8---

While it works for the 3 first lists, the last one stays empty (while
I should see, there, the most of my actions to do).

Is this a bug?

Best regards,
  Seb

-- 
Sebastien Vauban