Question on projectile code.

When a new projectile is added to the simulation, the script code sets (normally) the reference to a source object.
(The object, that fired the projectile).

The source object is looked up on the server in the Projectile::onAdd() method:

if (Sim::findObject(mSourceObjectId, ptr))

and replicated to the clients in Projectile::unpackUpdate():

NetObject* pObject = con->resolveGhost(mSourceObjectId);

However, after a constant time: SourceIdTimeoutTicks (7 ticks = 231 ms),
the source object reference is cleared in Projectile::processTick()

if(mSourceObject && mCurrTick > SourceIdTimeoutTicks)
{
	mSourceObject = 0;
	mSourceObjectId = 0;
}

This is independent of the lifetime of the projectile and leads to situations, where the projectile is still alive and processed, while the source object reference has already been cleared.
For my projectile subclass (a laser beam) this leads to some problems, since I am constantly requesting some infos from the source object, e.g. position, speed, ....

So my question is: What is the intention of the above code?
Why is it necessary to clear the source object reference and why is it necessary to do this at a fixed time, even if the projectile is still alive?

Of course I can change the code to clear the reference when the projectiles lifetime has expired, but I want to make sure, that there are no side effects.

Thanks
-- Markus