[TLF 2609202] RTE when trying to delete a LinkElement in a RichEditableText control

Found in 4.1.0.15465

Steps to reproduce:
1. Compile and run attached .MXML file.

<?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">

<s:RichEditableText width="400" height="100"
horizontalCenter="0" verticalCenter="0">
<s:textFlow>
<s:TextFlow>
<s>This is <s:span color="#FF0000">HTML text</s:span>
in an <s:span fontWeight="bold">Spark TextArea control</s:span>.
Use the <s:span textDecoration="underline">content</s:span> property
of the <s:span color="#008800">Spark TextArea control</s:span>
to include basic HTML markup in your text, including
<s:a>links</s:a>.
</s>
</s:TextFlow>
</s:textFlow>
</s:RichEditableText>

</s:Application>

2. Start deleting the text.

Actual Results:
When you start deleting the hyperlink, you get an RTE:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at flashx.textLayout.elements::FlowLeafElement/computeElementFormat()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\FlowLeafElement.as:398]
at flashx.textLayout.elements::FlowLeafElement/http://ns.adobe.com/textLayout/internal/2008::createContentElement()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\FlowLeafElement.as:92]
at flashx.textLayout.elements::SpanElement/http://ns.adobe.com/textLayout/internal/2008::createContentElement()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\SpanElement.as:81]
at flashx.textLayout.elements::FlowLeafElement/http://ns.adobe.com/textLayout/internal/2008::setParentAndRelativeStart()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\FlowLeafElement.as:179]
at flashx.textLayout.elements::FlowGroupElement/replaceChildren()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\FlowGroupElement.as:809]
at Function/http://adobe.com/AS3/2006/builtin::apply()
at flashx.textLayout.elements::SubParagraphGroupElement/replaceChildren()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\SubParagraphGroupElement.as:234]
at flashx.textLayout.elements::FlowGroupElement/deepCopy()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\FlowGroupElement.as:79]
at flashx.textLayout.elements::FlowGroupElement/deepCopy()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\FlowGroupElement.as:78]
at flashx.textLayout.elements::FlowGroupElement/deepCopy()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\elements\FlowGroupElement.as:78]
at flashx.textLayout.edit::TextFlowEdit$/createTextScrap()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\edit\TextFlowEdit.as:438]
at flashx.textLayout.operations::DeleteTextOperation/doOperation()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\operations\DeleteTextOperation.as:110]
at flashx.textLayout.edit::EditManager/doInternal()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\edit\EditManager.as:587]
at flashx.textLayout.edit::EditManager/doOperation()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\edit\EditManager.as:462]
at flashx.textLayout.edit::EditManager/deletePreviousCharacter()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\edit\EditManager.as:1050]
at flashx.textLayout.edit::EditManager/keyDownHandler()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\edit\EditManager.as:308]
at flashx.textLayout.container::ContainerController/keyDownHandler()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\container\ContainerController.as:2226]
at flashx.textLayout.container::TextContainerManager/keyDownHandler()[C:\Vellum\branches\v1\1.1\dev\output\openSource\textLayout\src\flashx\textLayout\container\TextContainerManager.as:1761]
at spark.components.supportClasses::RichEditableTextContainerManager/keyDownHandler()[E:\dev\4.x\frameworks\projects\spark\src\spark\components\supportClasses\RichEditableTextContainerManager.as:640]

Expected Results:
No RTE.

Workaround (if any):
n/a