[PATCH 2 of 3] Style: use ngx_str_null()

[cubicdaiya at gmail.com]

# HG changeset patch
# User Tatsuhiko Kubo <cubicdaiya at gmail.com>
# Date 1404915734 -32400
#      Wed Jul 09 23:22:14 2014 +0900
# Node ID f166c521b619dab231b15e60cec47dd81f52833e
# Parent  09e734739e462555dda00fb4cd420bdb07853cb7
Style: use ngx_str_null().

diff -r 09e734739e46 -r f166c521b619 src/core/ngx_resolver.c
--- a/src/core/ngx_resolver.c	Wed Jul 09 23:20:40 2014 +0900
+++ b/src/core/ngx_resolver.c	Wed Jul 09 23:22:14 2014 +0900
@@ -2722,8 +2722,7 @@
     }
 
     if (len == -1) {
-        name->len = 0;
-        name->data = NULL;
+        ngx_str_null(name);
         return NGX_OK;
     }