Milter-greylist

Trivial bugfix:

Index: acl.c
===================================================================
RCS file: /milter-greylist/milter-greylist/acl.c,v
retrieving revision 1.63
diff -u -r1.63 acl.c
--- acl.c	9 May 2007 19:55:29 -0000	1.63
+++ acl.c	20 May 2007 15:41:44 -0000
@@ -892,6 +892,8 @@
 	char *buf;
 	size_t len;
 {
+	if (len > 0)
+		buf[0] = '\0';
 	return buf;
 }