Vaadin 8 – ComboBox.NewItemHandler loses items list

NewItemHandler seems to lose the items list under certain circumstances. Can be
reproduced with self-contained code attached that basically reflects the example of
the tutorial (by the way the method select() of the tutorial does not exists,
and was replaced by setSelectedItem()).

If Confirm new planets is not checked, everything works normal (as in the
tutorial that works), but if it is checked, thus insertion is confirmed through
a modal dialog – that in most cases is convenient – then the list is cleared and
only the inserted planet appears.

Curious – even if the dialog is canceled the list is cleared. It appears as if
NewItemHandler is vulnerable to modal dialogs (or focus lost?).

But actually the list is there, simply not shown. Calling markAsDirty is also
useless.

Any idea on how to prevent or bypass?