PrimingEvent. WTF?

I have been getting some weird issues with Scripter in 10.4.4, I didn't notice before, but that doesn't mean it wasn't happening before. Basically when I hit the run script button, some kind of strange "empty" midi event is called into the HandleMIDI() function at that time. ???

Having a look inside EventTypes.js, I see an object defined called PrimingEvent, and this appears to be what it is. But what is it?

From EventTypes.js:

//-----------------------------------------------------------------------------
// PrimingEvent : { }
//-----------------------------------------------------------------------------
PrimingEvent.prototype = new Event();
PrimingEvent.prototype.constructor = PrimingEvent;
//-----------------------------------------------------------------------------
function PrimingEvent(e) {
 this.value = 0;
 this.beatPos = 0;
 this.isRealtime = false;
};

//-----------------------------------------------------------------------------
PrimingEvent.prototype.toString = function() {
 return '';
};

In some cases in order to avoid problems in my HandleMIDI code I'm having to check to see if the event is the blank PrimingEvent obj before doing anything, which is really annoying. does anyone know anything about what this is?