sw: missing nullptr check
sw: missing nullptr check

As pointed out by JunitTest_sw_unoapi.

Change-Id: Ia553dfb48215fab44f4899223c63ee454ff1c648

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