Really small Spark Label throws RTE (whether it has text or not)

Found in 4.5.0.18064 (able to repro in 4.0 and 4.1, not a regression)

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

Actual Results:
BOOOOOOOOOOM!

ReferenceError: Error #1069: Property -1 not found on _AS3_.vec.Vector.<flash.display::DisplayObject> and there is no default value.
at spark.components::Label/truncateText()[E:\dev\4.0.0\frameworks\projects\spark\src\spark\components\Label.as:1246]
at spark.components::Label/http://www.adobe.com/2006/flex/mx/internal::composeTextLines()[E:\dev\4.0.0\frameworks\projects\spark\src\spark\components\Label.as:485]
at spark.components.supportClasses::TextBase/updateDisplayList()[E:\dev\4.0.0\frameworks\projects\spark\src\spark\components\supportClasses\TextBase.as:684]
at mx.core::UIComponent/validateDisplayList()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\core\UIComponent.as:8531]
at mx.managers::LayoutManager/validateDisplayList()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\managers\LayoutManager.as:663]
at mx.managers::LayoutManager/doPhasedInstantiation()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\managers\LayoutManager.as:718]
at mx.managers::LayoutManager/doPhasedInstantiationCallback()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\managers\LayoutManager.as:1072]

Expected Results:
No RTE, man.

Workaround (if any):
Dont make your s|Label so small, bub.
Or don't set maxDisplayedLines="1"