Always return refreshed category

* org-icalendar.el (org-print-icalendar-entries): Do not manually
  refresh categories.

* org-clock.el (org-clock-insert-selection-line): Do not manually
  refresh categories.

* org.el (org-get-category): Refresh categories if no category found.
(org-entry-properties): Do not manually refresh categories.
(org-prepare-agenda-buffers): Do not manually refresh categories.

It seems a very bad thing to call manually for a category refresh. It
seems better to try to refresh if we do not have a category.

Signed-off-by: Julien Danjou <julien@danjou.info>

lisp/org-archive.el

@@ -226,7 +226,6 @@ this heading."
       (save-excursion
 	(org-back-to-heading t)
 	;; Get context information that will be lost by moving the tree
-	(org-refresh-category-properties)
 	(setq category (org-get-category)
 	      todo (and (looking-at org-todo-line-regexp)
 			(match-string 2))

lisp/org-clock.el

@@ -442,9 +442,7 @@ pointing to it."
 	    (ignore-errors
 	      (goto-char marker)
 	      (setq file (buffer-file-name (marker-buffer marker))
-		    cat (or (org-get-category)
-			    (progn (org-refresh-category-properties)
-				   (org-get-category)))
+		    cat (org-get-category)
 		    heading (org-get-heading 'notags)
 		    prefix (save-excursion
 			     (org-back-to-heading t)

lisp/org-icalendar.el

@@ -302,7 +302,6 @@ When COMBINE is non nil, add the category to each line."
 	scheduledp deadlinep todo prefix due start
 	tmp pri categories location summary desc uid alarm
 	(sexp-buffer (get-buffer-create "*ical-tmp*")))
-    (org-refresh-category-properties)
     (save-excursion
       (goto-char (point-min))
       (while (re-search-forward re1 nil t)

lisp/org.el

@@ -8142,7 +8142,11 @@ call CMD."
 
 (defun org-get-category (&optional pos)
   "Get the category applying to position POS."
-  (get-text-property (or pos (point)) 'org-category))
+  (let ((pos (or pos (point))))
+    (or (get-text-property pos 'org-category)
+	(progn
+	  (org-refresh-category-properties)
+	  (get-text-property pos 'org-category)))))
 
 (defun org-refresh-category-properties ()
   "Refresh category text properties in the buffer."
@@ -13482,10 +13486,7 @@ things up because then unnecessary parsing is avoided."
 						       'add_times))
 		    props))
 	  (unless (assoc "CATEGORY" props)
-	    (setq value (or (org-get-category)
-			    (progn (org-refresh-category-properties)
-				   (org-get-category))))
-	    (push (cons "CATEGORY" value) props))
+	    (push (cons "CATEGORY" (org-get-category)) props))
 	  (append sum-props (nreverse props)))))))
 
 (defun org-entry-get (pom property &optional inherit literal-nil)
@@ -15702,7 +15703,6 @@ When a buffer is unmodified, it is just killed.  When modified, it is saved
 	      (set-buffer (org-get-agenda-file-buffer file)))
 	    (widen)
 	    (setq bmp (buffer-modified-p))
-	    (org-refresh-category-properties)
 	    (setq org-todo-keywords-for-agenda
 		  (append org-todo-keywords-for-agenda org-todo-keywords-1))
 	    (setq org-done-keywords-for-agenda