Element with null parent

Just wondering if this method of adding the property to the ClassInfo will construct a valid ElementProperty?

https://github.com/highsource/jaxb2-basics/blob/master/basic/src/main/java/org/jvnet/jaxb2_commons/plugin/simplify/SimplifyPlugin.java#L167

The source of `com.sun.tools.xjc.model.CClassInfo` suggests that one should call `addProperty` for it to be setup correctly. The `setParent` method on `CPropertyInfo` is package scoped and hence cannot be called outside.

```java
public void addProperty(CPropertyInfo prop) {
if(prop.ref().isEmpty())
// this property isn't contributing anything
// this happens when you try to map an empty sequence to a property
return;
prop.setParent(this);
properties.add(prop);
}
```