inline widget error on downcast

Here's the bug I found related to widgets that I was trying to add to trac:

A widget that has the property `inline:true` throws an error when it's downcast.
Here are the steps to reproduce:
1. create a simple widget:

CKEDITOR.plugins.add( 'a', {
    requires: 'widget',

    init: function( editor ) {
        editor.widgets.add( 'a', {
            allowedContent: 'div(!qqq);',
            requiredContent: 'div(qqq)',
            inline: true,
            template: '<div class="qqq"></div>',
            upcast: function( element ) {
                return element.name == 'div' && element.hasClass( 'qqq' );
            },
        } );
    }
} );

2. insert the widget html into the editor so that it's upcast to widget:

<textarea name="asd" id="rich">&lt;div class="qqq">initial text&lt;/div></textarea>

3. trigger the widget downcast:

editor.getData()

The error is `Uncaught TypeError: Cannot read property 'attributes' of null` in widget/plugin.js line 2282

Using ckeditor 4.3.3 full + widget downloaded from the online builder page.