1. M-x find-library RET vc-dir.el
2. C-s defcustom
3. C-M-x.  Note the following backtrace.

,----
| Debugger entered--Lisp error: (invalid-function (\, (lambda nil nil)))
|   (\, (lambda nil nil))()
|   funcall((\, (lambda nil nil)))
|   eval((funcall (function (\, (lambda nil nil)))) t)
|   eval-defun-1((custom-declare-variable (quote vc-dir-mode-hook) (\` (funcall (function (\, (lambda nil nil))))) "Normal hook run by `vc-dir-mode'.\nSee `run-hooks'." :type (quote hook) :group (quote vc)))
|   eval-defun-2()
|   eval-defun(nil)
|   call-interactively(eval-defun nil nil)
`----

It looks to me that it is an issue of orphaned "comma".

4. I am attaching a fix.

Hopefully it is OK.

ps: My next commit will come with all the ceremony.  Until then ...
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