Don't add modes to which-func-modes if already set to t.

* lisp/progmodes/verilog-mode.el (verilog-mode): Check whether
  which-func-modes is t before adding verilog-mode.
  Reported by Andy Moreton <andrewjmoreton@gmail.com>.

* lisp/mh-e/mh-folder.el (top): Check whether which-func-modes
  is t before adding mh-folder-mode.

1 files changed, 1 insertions, 1 deletions

diff --git a/lisp/progmodes/verilog-mode.el b/lisp/progmodes/verilog-mode.el
index c8ef8f0324c..0139795dd38 100644
--- a/lisp/progmodes/verilog-mode.el
+++ b/lisp/progmodes/verilog-mode.el
@@ -3592,7 +3592,7 @@ Key bindings specific to `verilog-mode-map' are:
   (set (make-local-variable 'imenu-generic-expression)
        verilog-imenu-generic-expression)
   ;; Tell which-func-modes that imenu knows about verilog
-  (when (boundp 'which-func-modes)
+  (when (and (boundp 'which-func-modes) (listp which-func-modes))
     (add-to-list 'which-func-modes 'verilog-mode))
   ;; hideshow support
   (when (boundp 'hs-special-modes-alist)