don't assert on export of ooo74510-1.odt to .docx
don't assert on export of ooo74510-1.odt to .docx

the math object is broken in the original .odt so we can't export its contents
as it doesn't have any

Change-Id: I8226cafed65b9e16a4aca6f48a4f711a55532975

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