You do appear to have one (blank) contact line/entry with a checkbox to the left.
You say this record is entirely empty, however, it is possible to create an almost empty contact record with a single space in one of the fields.
Whilst it doesn't seem possible to easily create an entirely empty contact record, you can edit that contact record, delete the space (or any data it might contain), save the record, and end up with an entirely blank contact record. Note that Gmail auto-saves contact records, so this could happen without you explicitly do so.
Presumably you can delete this "blank" entry to have an entirely empty contacts list?