org-habit: "++" render wrong color

[Yasushi SHOJI <yashi@atmark-techno.com>]

Hi all,

Since 5d19c2c6891acd55dae36fccc07defe359a7283e, the habit consistency
graph renders intervals in wrong color if you use `++'.

http://ibin.co/2V80yaYqOT1O

The above graph in the pic is from 5d19c2c68~1, the below is the tip
of master.  Note that red region from the left most `*' to `!' at the
bad line.

Here is an ECM:

#+BEGIN_SRC lisp
  (add-to-list 'load-path "~/src/org-mode/lisp")
  (require 'org)
  (add-to-list 'org-modules 'org-habit)
  (setq org-agenda-files '("/tmp/a.org"))
  (org-agenda-list)
#+END_SRC

#+BEGIN_SRC org
* TODO bad
  SCHEDULED: <2016-01-27 Wed ++1w>
  :PROPERTIES:
  :STYLE:    habit
  :END:
  - State "DONE"       from "TODO"       [2016-01-20 Wed 14:50]
  - State "DONE"       from "TODO"       [2016-01-13 Wed 14:50]

* TODO good
  SCHEDULED: <2016-01-27 Wed .+1w>
  :PROPERTIES:
  :STYLE:    habit
  :END:
  - State "DONE"       from "TODO"       [2016-01-20 Wed 14:50]
  - State "DONE"       from "TODO"       [2016-01-13 Wed 14:50]
#+END_SRC
-- 
            yashi