LOCATION_DEFAULT has no fallback, so missing coordinates return as success #46

Follow-on from #41, which covers the same failure mode in a different section.

LOCATION_DEFAULT currently returns lat/lng correctly. Unlike AMENITIES_DEFAULT and HIGHLIGHTS_DEFAULT, though, it has no recovery path — so if Airbnb stubs that section the way it stubbed the others, the tool will return a LOCATION_DEFAULT entry with no coordinates and still report success. A caller cannot tell "no coordinates published" from "extraction broke."

The coordinates are also carried at data.node.location.coordinate.{latitude,longitude}, which sits outside pdpPresentation and so survives independently of it. Verified on listing 1576852203737322823: both paths give 45.3535, -121.9452.

Cheap to guard against, and it seemed worth flagging before it breaks rather than after. Happy to follow whatever error convention you prefer here.