block reading for level events

src/http/ngx_http_request_body.c

diff --git a/src/http/ngx_http_request_body.c b/src/http/ngx_http_request_body.c
index e3094dd..fdb49c9 100644
--- a/src/http/ngx_http_request_body.c
+++ b/src/http/ngx_http_request_body.c
@@ -503,6 +503,7 @@
 
     do {
         if (r->headers_in.content_length_n == 0) {
+            r->read_event_handler = ngx_http_block_reading;
             return NGX_OK;
         }