ChoiceItem radio buttons are duplicated when using callbacks

[PierreRaybaut]

Description

When using the ChoiceItem component with a callback in a DataSet, and displaying
the DataSet with a DataSetEditGroupBox, the radio buttons are duplicated when the
callback is triggered at initialization.

Solution

During initialization, the DataSetEditGroupBox calls the DataSet's get method
which triggers the callback and reinitializes the ChoiceItem widget. The radio
buttons are then destroyed and recreated, but the old ones are still visible (their
destruction is handled but in a deferred way).

This can be fixed by simply hiding those old radio buttons in the meantime.