Update send event listener to detect invalid messages

[Renegade334]

The irc.sent listener in Bot::registerClientSubscribers() should check for an invalid message (parser>=2.0) as well as null.

Blocked until a client version is released that requires parser>=2.0.

[elazar]

Related client milestone: https://github.com/phergie/phergie-irc-client-react/milestones/2.2