[O] [BUG] No agenda column view summary shown if org-agenda-overriding-header is set

[Matt Lundin]

I find that column view summaries do not display if
org-agenda-overriding-header is set.

Steps to replicate:

emacs -Q -l ~/minimal.el

Where minimal.el contains...

--8<---------------cut here---------------start------------->8---
(add-to-list 'load-path "~/org-mode/lisp/")
(add-to-list 'load-path "~/org-mode/contrib/lisp/")

(require 'org)

(setq org-agenda-files '("~/test.org"))

(setq org-columns-default-format
      "%40ITEM(Task) %8Effort(Estimate){:} %8CLOCKSUM %20SCHEDULED %20DEADLINE 
%20TIMESTAMP")

(setq org-agenda-custom-commands
      '(("o" todo "TODO"
         ((org-agenda-overriding-header "Now")))))
--8<---------------cut here---------------end--------------->8---

...and ~/test.org contains...

--8<---------------cut here---------------start------------->8---
* TODO Buy groceries
  SCHEDULED: <2017-01-16 Mon>
  :PROPERTIES:
  :Effort:   0:10
  :END:
  [2017-01-16 Mon 15:11]
* TODO Mow lawn
  SCHEDULED: <2017-01-16 Mon>
  [2017-01-16 Mon 15:11]
* TODO Clean house
  SCHEDULED: <2017-01-16 Mon>
  [2017-01-16 Mon 15:11]
--8<---------------cut here---------------end--------------->8---

When calling column view, the overlay summary line with total effort
estimates is missing.

I ran a git bisect and determined that this bug was introduced with
commit 279902ca4da4fe5f0ceff801a3aab51b942b42b7 (Feb. 14, 2016).
Versions of org before this correctly display the summary line.

Best,
Matt