Fix for trackCollision(e), can now be done on first execution

[DerelictDrone]

Switches check for registered_chips[self.entity] (which is reliant on the constructor running) to self.entity.registered_events["entityCollision"] which appears to be populated by the compiler / e2 upload, and is available before first execution of chip (before constructors are run).

Not extensively tested, but upon initial inspection, fixes code like

interval(500)
if( first() ){
    E = entity():isWeldedTo()
    trackCollision(E) // Runtime error - event entityCollision is needed
}

print( isTrackingCollision(E) )

event entityCollision(Entity:entity, HitEntity:entity, CollisionData:collision) {
    print("event", Entity)
}