fix segfault when a request body fits in r->header_in and
the body will be written to file
diff --git a/src/http/ngx_http_request_body.c b/src/http/ngx_http_request_body.c
index f5f8275..11f82db 100644
--- a/src/http/ngx_http_request_body.c
+++ b/src/http/ngx_http_request_body.c
@@ -163,6 +163,8 @@
 
             /* the whole request body may be placed in r->header_in */
 
+            rb->to_write = rb->bufs;
+
             r->read_event_handler = ngx_http_read_client_request_body_handler;
 
             return ngx_http_do_read_client_request_body(r);