fix: send volatile packets with binary attachments

The binary attachments of volatile packets were discarded (only the
header packet was sent) due to a bug introduced by [1].

Related: https://github.com/socketio/socket.io/issues/3919

[1]: https://github.com/socketio/socket.io/commit/dc381b72c6b2f8172001dedd84116122e4cc95b3