avoid out of bounds string access
avoid out of bounds string access

Change-Id: I0a0affea08528fc9bd729ab01cdb5fa6e9f8e18f

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