In the VarSet dialog, we can create an editor after the name and type
has been determined. However, if the name is changed after an editor
has been created, the editor is invalid because the underlying property
has been removed. In that case, the function onNameDetermined() should
clean up the invalid editor and this happens in most cases.
Unfortunately, it cannot handle the case in which a click happens on the
invalid editor itself. This click should result in onNameDetermined() but
since the editor is already invalid, onNameDetermined() is triggered too
late.
The current commit solves this by listening for every change in the name
of the property and handle the editors accordingly.
