What is the cleanest way to have "Empty" option in a combobox in Extjs6?
<p>I have a basic combobox backed by an ajax store. I want to be able to select an empty value from the combo as an option (it doesn't exist as a record in a store). Setting <code>emptyText: 'None'</code> would be perfect, the only problem is that once you selected some value you can't select an empty one anymore. </p>

<p>Is there a better option than listening to store load and injecting extra empty records, or something of that nature. I don't want to permanently have empty records in that store, only when used in certain comboboxes.</p>

<pre><code>{
    xtype: 'combo',
    queryMode: 'local',
    triggerAction: 'all',
    forceSelection: true,
    editable: false,
    emptyText: 'None',
    store: 'MyStore',
}
</code></pre>