HTTP/2: fixed the "http request count is zero" alert. When the stream is terminated the HEADERS frame can still wait in the output queue. This frame can't be removed and must be sent to the client anyway, since HTTP/2 uses stateful compression for headers. So in order to postpone closing and freeing memory of such stream the special close stream handler is set to the write event. After the HEADERS frame is sent the write event is called and the stream will be finally closed. Some events like receiving a RST_STREAM can trigger the read handler of such stream in closing state and cause unexpected processing that can result in another attempt to finalize the request. To prevent it the read handler is now set to ngx_http_empty_handler. Thanks to Amazon.

--- a/src/http/v2/ngx_http_v2.c
+++ b/src/http/v2/ngx_http_v2.c
@@ -3935,6 +3935,7 @@ ngx_http_v2_close_stream(ngx_http_v2_str
 
     if (stream->queued) {
         fc->write->handler = ngx_http_v2_close_stream_handler;
+        fc->read->handler = ngx_http_empty_handler;
         return;
     }