bug#4052: Emacs hangs with C-u C-u lrgep

Emacs hangs and every keystroke beeps with error messages like

  cd: Wrong type argument: stringp, nil
  file-remote-p: Wrong type argument: stringp, nil

because `C-u C-u M-x lrgep M-p RET' sets `default-directory' to nil.

I believe this is the correct fix:

Index: lisp/progmodes/grep.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/progmodes/grep.el,v
retrieving revision 1.102
diff -u -r1.102 grep.el
--- lisp/progmodes/grep.el	8 Jul 2009 14:24:00 -0000	1.102
+++ lisp/progmodes/grep.el	5 Aug 2009 22:17:36 -0000
@@ -827,7 +827,7 @@
 					  command nil nil 'grep-history))
 	    (add-to-history 'grep-history command))))
       (when command
-	(let ((default-directory dir))
+	(let ((default-directory (or dir default-directory)))
 	  ;; Setting process-setup-function makes exit-message-function work
 	  ;; even when async processes aren't supported.
 	  (compilation-start (if (and grep-use-null-device null-device)

-- 
Juri Linkov
http://www.jurta.org/emacs/