From 6a8f71e7eb96d885421b16c96df125ea4c11a4aa Mon Sep 17 00:00:00 2001
From: Karl Heuer <kwzh@gnu.org>
Date: Fri, 25 Feb 1994 03:24:15 +0000
Subject: [PATCH] (set-visited-file-name): Unlock the file if setting the
 visited file name to nil.

---
 lisp/files.el | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lisp/files.el b/lisp/files.el
index aac5ebb1a64..1ca1369d250 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -1151,9 +1151,8 @@ if you wish to pass an empty string as the argument."
 		nil
 	      (expand-file-name filename))))
   (or (equal filename buffer-file-name)
-      (null filename)
       (progn
-	(lock-buffer filename)
+	(and filename (lock-buffer filename))
 	(unlock-buffer)))
   (setq buffer-file-name filename)
   (if filename				; make buffer name reflect filename.