(match-string): Delete extra arg to buffer-substring.

lisp/subr.el

@@ -888,7 +888,7 @@ If the last search or match was done against a string,
 specify that string as the second argument STRING."
   (if string
       (substring string (match-beginning 0) (match-end 0))
-    (buffer-substring string (match-beginning 0) (match-end 0))))
+    (buffer-substring (match-beginning 0) (match-end 0))))
 
 (defun shell-quote-argument (argument)
   "Quote an argument for passing as argument to an inferior shell."