fix crash after conversion to STL
fix crash after conversion to STL

Change-Id: I0a49ce4ddf53eede0f940b392aab20afb5dd2cbe

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core