Fix 'single directory radio' widget with 'onchange' custom property when used in list or complex field

How to reproduce in the JSF UI:

• in Studio create a new document type
• add a complex field
• in the complex field, add a Directory field linked to *directory nature
• define the create layout and use a single directory radio widget for the Directory field
• add a custom property to the single directory radio widget named onchange and value alert(this.value);
• deploy to a Nuxeo instance

The alert that is supposed to happen when a selection is done on the single directory radio widget does not happen.
The same problem occurs in a multivalued complex field.

The problem does NOT occur, and the alert is rendered, when a single directory radio widget is used for a field not in a complex field or a multivalued complex field (at the top-level of the schema i.e. for field field1 in screenshot below).