Code:
@Override
    public Widget asWidget() {


        VerticalLayoutContainer c = new VerticalLayoutContainer();


        List<String> choice = Arrays.asList(null, "1", "2", "3");


        ListStore<String> choiceStore = new ListStore<String>(new ModelKeyProvider<String>() {


            @Override
            public String getKey(String pItem) {
                return pItem;
            }
        });


        choiceStore.addAll(choice);
        
        ComboBox<String> cb = new ComboBox<String>(choiceStore, new LabelProvider<String>() {


            @Override
            public String getLabel(String pItem) {
                return pItem;
            }
        });
        
        c.add(cb);


        return c;
    }
Expected:
When I navigate the ComboBox dropdown list with the arrow keys and press enter while the desired value is highlighted, the ComboBox should collapse and display the selected value.

Actual:
Selection works well for the values 1, 2 and 3. Selecting the null value by pressing the enter key does not work. The ComboBox does not collapse.