coverity#1256663: sw: fix Ring::equals()
coverity#1256663: sw: fix Ring::equals()

Change-Id: I199ad135fcb217866e8daa0797f4013f8acf4f6a

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