Fix default purchase correction to use recorded location instead of org default

GitHub Issue #5536 - rubyforgood/human-essentials When correcting a purchase, the storage location dropdown incorrectly defaults to the organization's default storage location, instead of the location recorded on the existing purchase. Root cause: The default_location helper in ApplicationHelper prioritizes current_organization.default_storage_location before checking the source object's storage_location_id. Fix: Reorder the logic to check the source object's storage_location_id first, falling back to the organization default only when no location is recorded on the purchase.