fmt: write empty or blocks the same as empty fn bodies, empty structs, etc (#9136)

vlib/x/websocket/websocket_test.v

@@ -48,7 +48,7 @@ fn start_server(listen_port int) ? {
 	s.on_close(fn (mut ws websocket.Client, code int, reason string) ? {
 		// not used
 	})
-	s.listen() or { }
+	s.listen() or {}
 }
 
 // ws_test tests connect to the websocket server from websocket client