Popping up a spark component in a spark Module causes RTE

Steps to reproduce:
1. Create a spark Application with a spark Module that pops up a SkinnableComponent.

Main.mxml:

<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
creationComplete="appModule.loadModule();">
<s:ModuleLoader id="appModule" url='module/Module.swf' width="100%" height="50%" />
</s:Application>

Module.mxml:

<s:Module xmlns:fx="http://ns.adobe.com/mxml/2009"
xmlns:s="library://ns.adobe.com/flex/spark"
width="100%" height="100%">

<fx:Script>
<![CDATA[
import mx.managers.PopUpManager;
private function openPopUp():void

{ PopUpManager.createPopUp(this.parentApplication.root, SomeCustomComponent); }

]]
>
</fx:Script>

<fx:Declarations>
<fx:Component className="SomeCustomComponent">
<s:Group>
<s:Button id="button" />
</s:Group>
</fx:Component>
</fx:Declarations>

<s:Button label="Open Popup" click="openPopUp()" />

</s:Module>

2. Click "Open Popup"

Actual Results:

RTE:

Error: Skin for SomeCustomComponent13.button cannot be found.
at spark.components.supportClasses::SkinnableComponent/attachSkin()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\supportClasses\SkinnableComponent.as:698]
at spark.components.supportClasses::SkinnableComponent/validateSkinChange()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\supportClasses\SkinnableComponent.as:443]
at spark.components.supportClasses::SkinnableComponent/createChildren()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\supportClasses\SkinnableComponent.as:406]
at mx.core::UIComponent/initialize()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\core\UIComponent.as:7624]
at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\core\UIComponent.as:7485]
at mx.core::UIComponent/addChildAt()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\core\UIComponent.as:7189]
at spark.components::Group/addDisplayObjectToDisplayList()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\Group.as:2037]
at spark.components::Group/http://www.adobe.com/2006/flex/mx/internal::elementAdded()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\Group.as:1628]
at spark.components::Group/setMXMLContent()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\Group.as:633]
at spark.components::Group/createChildren()[E:\dev\4.5.1\frameworks\projects\spark\src\spark\components\Group.as:855]
at mx.core::UIComponent/initialize()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\core\UIComponent.as:7624]
at module::SomeCustomComponent/initialize()
at mx.managers.systemClasses::ChildManager/childAdded()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\systemClasses\ChildManager.as:189]
at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::rawChildren_addChildAt()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\SystemManager.as:2139]
at mx.managers::SystemManager/addChildAt()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\SystemManager.as:1759]
at mx.managers::SystemManager/addChild()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\SystemManager.as:1742]
at mx.managers::PopUpManagerImpl/addPopUp()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\PopUpManagerImpl.as:340]
at mx.managers::PopUpManagerImpl/createPopUp()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\PopUpManagerImpl.as:229]
at mx.managers::PopUpManager$/createPopUp()[E:\dev\4.5.1\frameworks\projects\framework\src\mx\managers\PopUpManager.as:139]
at module::Module/openPopUp()[/Users/stshongr/Desktop/test/src/module/Module.mxml:10]
at module::Module/___Module_Button1_click()[/Users/stshongr/Desktop/test/src/module/Module.mxml:23]

It appears that the Button in the popup is not getting its skin applied which is causing this RTE.

Expected Results:

No RTE

Workaround (if any):

Add a Button in the main application (not the module) and set that it is not include in the layout and that it is invisible:

<?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"
creationComplete="appModule.loadModule();">
<s:Button includeInLayout="false" visible="false" />
<s:ModuleLoader id="appModule" url='module/Module.swf' width="100%" height="50%" />
</s:Application>

I'm not sure if this is a valid workaround since if the user has a few SkinnableComponents in the module's pop up (like RadioButton, CheckBox, etc.) they all need to be defined as invisible in the main app.