remove useless null pointer checks before delete
remove useless null pointer checks before delete

Change-Id: I33ba84aebcb8d8abec4af13f9c0bb12a3364d8de

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