Returning False Instead of Empty Array for Countries Without States

Right now if you go to the checkout page for a country without states (like the UK) there is a text field but no pre entered data. You have to retype in the county data (Ugh!). If you return `false` in `get_states` instead of an empty array you correctly hit the `else` conditional in `woocommerce_form_field`.
https://github.com/woothemes/woocommerce/blob/v2.1.3/includes/wc-template-functions.php#L1696-L1705

Ref: https://woothemes.zendesk.com/agent/#/tickets/152959