don't crash on export of fdo60087-2.xlsx to xls
don't crash on export of fdo60087-2.xlsx to xls

Change-Id: I888828bc88deea16c46895d29f25526bd3c44ce7

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