No, that's ok, because `removeInstanceFromPool` works with that `null` value. The only thing I can see here is with `addInstancePool` that it overwrites `null` values, but I guess that's also ok, because in the old code it throws a fatal error, because of this https://github.com/propelorm/Propel2/blob/master/src/Propel/Runtime/ActiveQuery/InstancePoolTrait.php#L24
So it looks like it already has been made sure that the `$object` for `addInstanceToPool` is the correct type.

Anyways, we should add there more docblocks and look through that code - but in a other #issue, please.