* bdx.el (bdx--occur): Fix compilation error on Emacs-27.

Author: mkcms

bdx.el

@@ -600,7 +600,8 @@ This turns a string of the form \\='function<type<T>>\\=' into
           (insert-row "type" type 'font-lock-type-face)
           (insert "\n")))))
 
-  (button-mode +1)
+  (when (fboundp 'button-mode)
+    (button-mode +1))
   (goto-char (point-min)))
 
 (ivy-configure 'bdx :occur #'bdx--occur)