<zk>
    <label multiline="true">
    1. Select "option 1" in the selectbox.
    2. Click "clear" button.
    3. Open and close the selectbox should not see NullPotinerException showed.
    </label>
    <div>
        <selectbox id="selbox" onSelect='System.out.println(self.getSelectedIndex())' />
        <button id="btn" label="clear" onClick="clear()" />
        <zscript><![CDATA[
        ListModelList lml = new ListModelList();
        lml.add("option 1");
        lml.add("option 2");
        lml.add("option 3");
        lml.add("option 4");
        lml.add("option 5");
        selbox.setModel(lml);
        
        void clear() {
            selbox.setModel(null);
        }
        ]]></zscript>
    </div>
</zk>