Lisp error: (wrong-type-argument stringp nil)

[Leo]

GNU Emacs 23.3.50.1 (x86_64-apple-darwin10.8.0, Carbon Version 1.6.0 AppKit 1038.36)
 of 2011-12-11 on localhost

I am getting an error when opening .hs files:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  string-match("[ \f	\n^M^K]+" nil 0)
  split-string(nil)
  haskell-flymake-init()
  flymake-start-syntax-check()
  flymake-after-save-hook()
  run-hooks(after-save-hook)
  basic-save-buffer()
  save-buffer(1)
  call-interactively(save-buffer nil nil)


_patch_:

--- a/haskell-mode.el
+++ a/haskell-mode.el
@@ -606,7 +606,8 @@
 (defun haskell-flymake-init ()
   "Flymake init function for Haskell.
 To be added to `flymake-init-create-temp-buffer-copy'."
-  (let ((checker-elts (split-string haskell-saved-check-command)))
+  (let ((checker-elts (and haskell-saved-check-command
+                          (split-string haskell-saved-check-command))))
     (list (car checker-elts)
          (append (cdr checker-elts)
                  (list (flymake-init-create-temp-buffer-copy