404 when loading API that does not include API specification document

[pierceboggan]

Reproduction Steps

1. Create a new API in API Center that does not contain an API specification document.
2. Open that API in API Center portal detail view.

Expected

API detail page loads appropriately.

Actual

API detail page fails to load due to missing specification on exportSpecification API call:
{
"title": "Not Found",
"status": 404
}