[NTG-context] about the default bullets of itemized lists

Dear all, It is not a big problem, but I don't know why this curious thing happened. A few days ago, I updated ConTeXt and made a format file for XeConTeXt. I run a file which was compiled well before and got a strange results: at this time. all the bullets of the itemized lists are gone(no bullets). After I changed the first \startitemize to \startitemize[1] only, then all the itemized lists in the whole text had a bullet again. If I changed [1] to [2] and [3], it disappeared again(including bullets for \head). Is this normal? or are there something wrong in my setup or in my document? Thank you for reading. Dalyoung