RTE when PopUp/Callout is defined in Declarations as a single instance

Steps to reproduce:
1. Create an app with the following code:

<?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" >

<fx:Declarations>
<s:Callout id="co1" width="200" height="200" />

</fx:Declarations>

<s:Button id="btn" click="co1.open(btn)" />

</s:Application>

2. Run the app.

Actual Results: RTE thrown:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at spark.components::Application$/get http://www.adobe.com/2006/flex/mx/internal::softKeyboardBehavior()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Application.as:1961]
at spark.components::SkinnablePopUpContainer()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\SkinnablePopUpContainer.as:164]
at spark.components::Callout()[E:\dev\4.y\frameworks\projects\mobilecomponents\src\spark\components\Callout.as:177]
at test02/_test02_Callout1_i()
at test02()[C:\Documents and Settings\ymachiya\Adobe Flash Builder 4.5\test02\src\test02.mxml:3]
at _test02_mx_managers_SystemManager/create()[_test02_mx_managers_SystemManager.as:51]
at mx.managers.systemClasses::ChildManager/initializeTopLevelWindow()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\systemClasses\ChildManager.as:311]
at mx.managers::SystemManager/initializeTopLevelWindow()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\SystemManager.as:3057]
at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::kickOff()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\SystemManager.as:2843]
at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::preloader_completeHandler()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\SystemManager.as:2723]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()
at mx.preloaders::Preloader/timerHandler()[E:\dev\4.y\frameworks\projects\framework\src\mx\preloaders\Preloader.as:542]
at flash.utils::Timer/_timerDispatch()
at flash.utils::Timer/tick()

Expected Results: Not sure when it broke but this is supposed to work according to the doc sample: http://help.adobe.com/en_US/flex/using/WS67cd75b2532ad652-1abb110512d5bda966d-8000.html

*NOTES* The case that a custom class is defined instead of the instance works:

<fx:Declarations className="MyCallout">
<s:Callout width="200" height="200" />
</fx:Declarations>

Workaround (if any):