Found few cases label value missing

Dear organizer,
I Found few cases mask value is 0. it is normal or i downloaded wrong data?. I have used previous dataset link.
thanks.

Thank you for your question.
As we state in the data description, a proportion of datasets have no lesions and thus all zero masks.

Thank you for your question.
As we state in the data description, a proportion of datasets have no lesions and thus all zero masks.

thanks for your reply.
best regards,
Moona