I was surprised that this was necessary; the documentation states:

```
For the Children mapping, cascading persist and remove are implicit 
and cannot be disabled. A PHPCR node always must have a parent, 
removing the parent removes its children. The child removal happens on 
PHPCR level and does not trigger additional lifecycle events.
```

Without adding `cascade="persist"` to the annotation, the code will throw an exception when a new child is found. Is the documentation wrong, or is this a separate bug?