Fix to allow selecting falsy values in dropdown-list type filter.
Fix to allow selecting falsy values in dropdown-list type filter.

When I added the `dropdown-list` filter type, I accidentally introduced a bad conditional here - we should compare specifically against `undefined` when determining whether to use the label as the value. The existing condition does not support valid defined values that evaluate to false (such as 0 or ‘’).

johnyanarella/radium-filters,jasongardnerlv/radium-filters