Bugfix/issue 27 invalid item access

[sam-cormack]

Fix for issue #27

Scheduled event handlers can run after a call to disconnect on the client. The conversation object has been cleared so item lookups cause an error to be thrown in some handlers.

With these changes, the event handler function returns early if the client is not connected, before trying to look up items.

A test case has been added, however the error triggers after the successful completion of the test. Not sure how to wait for all scheduled event handlers to run in the test.

[minons1]

cmiiw, I believe that isConnected() is not reflecting the status of the websocket connection, since when the websocket is closed without calling client.close() method, isConnected() will still resolve to true?

So the better way to check isConnected() is by validating the wsClient.readyState?

[sam-cormack]

That's true, but it's the state of the conversation object that I'm really trying to check rather than the websocket connection. I don't think there's any issue if the event handlers run after the websocket disconnects (though I could be wrong about that). conversation.clear() is only called alongside realtime.disconnect() at the moment so checking realtime.isConnected() does the job. It's probably not ideal, since conversation.clear() could get called elsewhere - even from client code.