spark radiobuttongroup does not support setting the selectedValue to null

Example below: select a radio button, click the Clear button, echo the selected radio button - still the value of the selected radio button.

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:mx="library://ns.adobe.com/flex/mx"
minWidth="955" minHeight="600">
<fx:Script>
<![CDATA[
import mx.controls.Alert;
]]
>
</fx:Script>

<fx:Declarations>
<s:RadioButtonGroup id="myGroup" />
</fx:Declarations>

<s:layout>
<s:VerticalLayout />
</s:layout>

<s:RadioButton value="value1" label="Value 1" group="

" />
<s:Button label="clear radio" click="myGroup.selectedValue = null;" />
<s:Button label="echo selected radio" click="Alert.show(myGroup.selectedValue as String);" />
</s:Application>

Clearing the selectedValue should both clear the selected value and uncheck all radio buttons.

Workaround is tough but possible because vars are private in radiobuttongroup (_selection).

This is a regression because mx radiobuttongroup allowed this.