Problem with Spark datagrid in flash builder 4.7

hi

I'm creating a project in fb 4.7 and now i am facing weird problem with spark.datagrid in specific in the columns headerText when i type it in Arabic with two words like "تاريخ الجلسة" i get this error:

RangeError: Error #1125: The index 0 is out of range 0.          at spark.components::Label/getNextTruncationPosition()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Label.as:1582]          at spark.components::Label/truncateText()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Label.as:1381]          at spark.components::Label/http://www.adobe.com/2006/flex/mx/internal::composeTextLines()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Label.as:491]          at spark.components.supportClasses::TextBase/updateDisplayList()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\supportClasses\TextBase.as:685]          at mx.core::UIComponent/validateDisplayList()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:8999]          at mx.managers::LayoutManager/validateClient()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\LayoutManager.as:1033]          at mx.core::UIComponent/validateNow()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:8077]          at spark.components.gridClasses::GridColumnHeaderGroupLayout/updateDisplayList()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\gridClasses\GridColumnHeaderGroupLayout.as:371]          at spark.components.supportClasses::GroupBase/updateDisplayList()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\supportClasses\GroupBase.as:1294]          at spark.components::Group/updateDisplayList()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Group.as:1117]          at mx.core::UIComponent/validateDisplayList()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:8999]          at spark.components::Group/validateDisplayList()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Group.as:1039]          at mx.managers::LayoutManager/validateDisplayList()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\LayoutManager.as:736]          at mx.managers::LayoutManager/doPhasedInstantiation()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\LayoutManager.as:801]          at mx.managers::LayoutManager/doPhasedInstantiationCallback()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\LayoutManager.as:1180] 

but when it's in english it's work perfect.

thanks.