OptionGroup addValueChangeListener CheckBox
<p>Vaadin 7.6.5. 
I am trying to figure out why a value change listener fails in the below case?
The CheckBox is observing for addValueChangeListener OptionGroup.</p>

<pre><code>@Theme("vaadindemo")
public class VaadindemoUI extends UI {

    @WebServlet(value = "/*", asyncSupported = true)
    @VaadinServletConfiguration(productionMode = false, ui = VaadindemoUI.class)
    public static class Servlet extends VaadinServlet {
    }

    @Override
    protected void init(VaadinRequest request) {
        final VerticalLayout layout = new VerticalLayout();
        layout.setMargin(true);
        setContent(layout);

        OptionGroup group = new OptionGroup();
        group.addItem("01");
        group.setItemCaption("01", "ONE");

        group.addItem("02");
        group.setItemCaption("02", "TWO");

        group.addItem("03");
        group.setItemCaption("03", "THREE");
        group.addValueChangeListener(new ValueChangeListener() {

            @Override
            public void valueChange(ValueChangeEvent event) {
                System.out.println("group getValue " + event.getProperty().getValue());
                System.out.println("group getType " + event.getProperty().getType());
            }
        });
        CheckBox box = new CheckBox();
        box.setCaption("Check Me");
        //Notify CheckBox of value change of radio button

        //group.addValueChangeListener(box); -- // Code Fails 
        //box.addValueChangeListener(group); // Selected Radio Button is removed  


        TextField field = new TextField();
        field.addValueChangeListener(new ValueChangeListener() {

            @Override
            public void valueChange(ValueChangeEvent event) {
                System.out.println("field getValue " + event.getProperty().getValue());
                System.out.println("field getType " + event.getProperty().getType());

                System.out.println("field getType " + field.getValue());
            }
        });


        group.addValueChangeListener(field);// The value is reflected. How do i get only the event without over writing the value

        //group.addValueChangeListener(box);

        layout.addComponent(group);
        layout.addComponent(box);
        layout.addComponent(field);

        Button button = new Button("Click Me");
        button.addClickListener(new Button.ClickListener() {
            public void buttonClick(ClickEvent event) {
                layout.addComponent(new Label("Thank you for clicking"));
            }
        });
        layout.addComponent(button);
    }

}
</code></pre>

<p>It logs:</p>

<pre>
com.vaadin.data.util.converter.Converter$ConversionException: Unable to convert value of type java.lang.String to presentation type class java.lang.Boolean. No converter is set and the types are not compatible.
    at com.vaadin.data.util.converter.ConverterUtil.convertFromModel(ConverterUtil.java:116)
    at com.vaadin.ui.AbstractField.convertFromModel(AbstractField.java:736)
    at com.vaadin.ui.AbstractField.convertFromModel(AbstractField.java:721)
    at ...
</pre>