make sure the denominator is not 0
make sure the denominator is not 0

Change-Id: Ic32e0f354bb290ad77f1d7709bee89858e1889b7

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