small fix for account nr validation
small fix for account nr validation

onepercentclub/bluebottle,onepercentclub/bluebottle,jfterpstra/bluebottle,jfterpstra/bluebottle,jfterpstra/bluebottle,onepercentclub/bluebottle,jfterpstra/bluebottle,onepercentclub/bluebottle,onepercentclub/bluebottle