ox-beamer: Fix "apply: Wrong number of arguments: max, 0"

* lisp/ox-beamer.el (org-beamer-select-environment): Use variable
  introduced in 4743d43.

Reported-by: Jarmo Hurri <jarmo.hurri@iki.fi>
<http://permalink.gmane.org/gmane.emacs.orgmode/106705>

lisp/ox-beamer.el

@@ -1107,7 +1107,7 @@ aid, but the tag does not have any semantic meaning."
   (let* ((envs (append org-beamer-environments-special
 		       org-beamer-environments-extra
 		       org-beamer-environments-default))
-	 (org-tag-alist
+	 (org-current-tag-alist
 	  (append '((:startgroup))
 		  (mapcar (lambda (e) (cons (concat "B_" (car e))
 				       (string-to-char (nth 1 e))))