colview: Ignore operators associated to special properties

* lisp/org-colview.el (org-columns--compute-spec): Ignore operator
associated to a special properties.

This is a followup to e1b8d1d2b4ef46e0c4ef591536a77eeeed45d998.

lisp/org-colview.el

@@ -1165,14 +1165,13 @@ properties drawers."
 	 (last-level lmax)
 	 (property (car spec))
 	 (printf (nth 4 spec))
-	 (operator (nth 3 spec))
+         ;; Special properties cannot be collected nor summarized, as
+         ;; they have their own way to be computed.  Therefore, ignore
+         ;; any operator attached to them.
+	 (operator (and (not (member property org-special-properties))
+                        (nth 3 spec)))
 	 (collect (and operator (org-columns--collect operator)))
-	 (summarize (and operator (org-columns--summarize operator)))
-         ;; Special properties are not set in a property drawer, and
-         ;; therefore should not be updated.
-         (update
-          (and update
-               (not (member property org-special-properties)))))
+	 (summarize (and operator (org-columns--summarize operator))))
     (org-with-wide-buffer
      ;; Find the region to compute.
      (goto-char org-columns-top-level-marker)