Win32: fixed build after cf3e75cfa951.

src/http/v2/ngx_http_v2_filter_module.c

diff --git a/src/http/v2/ngx_http_v2_filter_module.c b/src/http/v2/ngx_http_v2_filter_module.c
index da78407..235a006 100644
--- a/src/http/v2/ngx_http_v2_filter_module.c
+++ b/src/http/v2/ngx_http_v2_filter_module.c
@@ -231,6 +231,10 @@
 
     server_tokens = clcf->server_tokens;
 
+#if (NGX_SUPPRESS_WARN)
+    ngx_str_null(&tokens);
+#endif
+
     if (r->headers_out.server == NULL) {
 
         if (server_tokens == 0) {