Make buttons in header lines work

* lisp/help-mode.el (help-button-action): `help-xref-button' in
header line doesn't work (bug#21024).

Backport:

(cherry picked from commit c11e565a6b6d09fa39d4c3ef65bef08190eaecc1)

diff --git a/lisp/help-mode.el b/lisp/help-mode.el
index e0f3351e67de4e07e1340640ded71936c409fde8..7b95e5fb04e195373974dc2423904b1f9ade86e8 100644 (file)
--- a/lisp/help-mode.el
+++ b/lisp/help-mode.el
@@ -107,7 +107,7 @@ The format is (FUNCTION ARGS...).")
 
 (defun help-button-action (button)
   "Call BUTTON's help function."
-  (help-do-xref (button-start button)
+  (help-do-xref nil
                (button-get button 'help-function)
                (button-get button 'help-args)))