Add error handling for single numbers

[CaptnCodr]

When a tracking number was sent to the customer the tracking number cannot be found in the system immediately (404) after creation.

• Add error handling, so that the list view is still available with a message for this single tracking number.

Message by system:

{
  "title": "No result found",
  "status": 404,
  "detail": "No shipment with given tracking number found."
}

Suggestion:
fsprojects/SwaggerProvider#132