Let org-agenda-time-grid control if the grid is displayed

* lisp/org-agenda.el (org-agenda-list): ensures that the
list returned by org-agenda-add-time-grid-maybe is appended
to rtnall before checking if rtnall is emtpy.

In the case where rtnall is empty (no item for current day),
we do not call org-agenda-add-time-grid-maybe.  This seems
bogus because that function is already computing whether the
time grid must be included, and does so according to the
user's preferences.

In particular, the org-agenda-time-grid variable has a
'require-timed' parameter controlling the visibility of the
time grid.

So, this patch :

 - removes the premature check for rtnall being empty,
 - inconditionally calls org-agenda-add-time-grid-maybe,
 - appends the result to rtnall,
 - and finally checks the emptiness of the resulting list
   before pretty printing.

TINYCHANGE
---
 lisp/org-agenda.el | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/lisp/org-agenda.el b/lisp/org-agenda.el
index cfd3e25..eebb66f 100644
--- a/lisp/org-agenda.el
+++ b/lisp/org-agenda.el
@@ -3886,10 +3886,11 @@ given in `org-agenda-start-on-weekday'."
 	    (put-text-property s (1- (point)) 'org-day-cnt day-cnt)
 	    (when todayp
 	      (put-text-property s (1- (point)) 'org-today t))
+	    (setq rtnall
+		  (append rtnall
+			  (org-agenda-add-time-grid-maybe rtnall ndays todayp)))
 	    (if rtnall (insert ;; all entries
-			(org-finalize-agenda-entries
-			 (org-agenda-add-time-grid-maybe
-			  rtnall ndays todayp))
+			(org-finalize-agenda-entries rtnall)
 			"\n"))
 	    (put-text-property s (1- (point)) 'day d)
 	    (put-text-property s (1- (point)) 'org-day-cnt day-cnt))))
-- 
1.7.10.2.484.gcd07cc5