check for valid string len
check for valid string len

as demonstrated by fdo59762-2.ods

Change-Id: I36cddaba5f664d5d95e9a661eed1cbe9dec1c273

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