Nested existing element cannot be linked to newly created object

[pmithrandir]

When you add an object, let's say a Father, you might add at the same time the kid or later on.

That works fine in this lib.

but if a father is created with an existing child (let say he is adopting) the script is lost. Script is trying to recreate the kid, even if the id is already defined.

That lead to an error.