An "IndexedPropertyChange" event gets delivered whenever a component that
conforms to the JavaBeans specification (a "bean") changes a bound
indexed property. This class is an extension of PropertyChangeEvent
but contains the index of the property that has changed.
Null values may be provided for the old and the new values if their
true values are not known.
An event source may send a null object as the name to indicate that an
arbitrary set of if its properties have changed. In this case the
old and new values should also be null.