check for empty string
check for empty string

as demonstrated by ooo29618-1.doc

Change-Id: I81c953530cd3a617a245ed03a9c355f3383045ab

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