Support null LogFactories.

I may be wrong, but it seems that in the constructor for Session there's code that both accesses the incoming logFactory and also checks it for null, but not in the right order:

constructor {
Log log = logFactory.create(sessionID);

try {
<snip>
if (logFactory != null)

{ state.setLog(log); }

log.onEvent("Session " + this.sessionID + " schedule is " + sessionSchedule);
}

seems like if it's possible for the logFactory to be null, that assumption should be tested on the earlier line as wel.