Revert "server _onHttpRequest(): ensure non-empty params"

This reverts commit 74d91390494becb06af12e1b353f21a81eb1bbfb.

Conflicts:
	server.js

feross commented on 74d9139 5 hours ago
> Do we need to check for empty params here?
>
> _onRequest should return an error via callback because
> params.action is missing. Won't that work?
https://github.com/feross/bittorrent-tracker/commit/74d91390494becb06af12e1b353f21a81eb1bbfb#commitcomment-8937428