[mod_fastcgi] fix return when streaming min buffer

fix incorrect return value when server.stream-response-body = 2

src/mod_fastcgi.c

@@ -368,7 +368,7 @@ static handler_t fcgi_recv_parse(server *srv, connection *con, struct http_respo
 	int fin = 0;
 
 	if (0 == n) {
-		if (!(fdevent_event_get_interest(srv->ev, hctx->fd) & FDEVENT_IN)) return 0;
+		if (!(fdevent_event_get_interest(srv->ev, hctx->fd) & FDEVENT_IN)) return HANDLER_GO_ON;
 		log_error_write(srv, __FILE__, __LINE__, "ssdsb",
 				"unexpected end-of-file (perhaps the fastcgi process died):",
 				"pid:", hctx->proc->pid,