Error 404 when requesting latest observation for valid stations using /stations/{stationId}/observations/latest

[rosteve]

Describe the bug
Is it expected to get error 404 when requesting for latest obeservations for a valid station?
Ideally, the result should be an empty list but no returning error 404 as its currently returning.

To Reproduce
To reproduce, use this API endpoint for SIOUX CENTER (COOPSIXI4):
https://api.weather.gov/stations/COOPSIXI4/observations/latest

Here's the response for the above request.
{
"correlationId": "5316761a",
"title": "Not Found",
"type": "https://api.weather.gov/problems/NotFound",
"status": 404,
"detail": "Not Found",
"instance": "https://api.weather.gov/requests/5316761a"
}

Expected behavior
It should return an empty list and not error 404.

Environment
Google Chrome Version 87.0.4280.88 (Official Build) (x86_64)

[scadergit]

Duplicate of #149