org-compat: Fix error on newest Emacsen (>= 25)

* lisp/org-compat.el (org-move-to-column): Ensure `remove' is called on
a list.

Reported-by: Julien Cubizolles <j.cubizolles@free.fr>
<http://permalink.gmane.org/gmane.emacs.orgmode/104703>

lisp/org-compat.el

@@ -333,7 +333,9 @@ Works on both Emacs and XEmacs."
 Pass COLUMN and FORCE to `move-to-column'.
 Pass BUFFER to the XEmacs version of `move-to-column'."
   (let ((buffer-invisibility-spec
-	 (remove '(org-filtered) buffer-invisibility-spec)))
+	 (if (listp buffer-invisibility-spec)
+	     (remove '(org-filtered) buffer-invisibility-spec)
+	   buffer-invisibility-spec)))
     (if (featurep 'xemacs)
 	(org-xemacs-without-invisibility
 	 (move-to-column column force buffer))