Relation catalog is empty after setting a new relation

I have items with fields, which reference other items. To keep the reference catalog up-to-date, I call an update method after an item of this type was created or modified.
Unfortunatly the references are not in the reference catalog after an item was created, although it is the same method which gets called as when an item was updated.
Does anyone have a idea how to fix this?

Gist: Code