Creating a network constituent for a non existing network throws

[mdoering]

Caused by: com.sun.jersey.api.client.UniformInterfaceException: HTTP 500: {"timestamp":"2021-04-26T15:09:24.855+00:00","status":500,"error":"Internal Server Error","message":"","path":"/https/github.com/network/029f9226-0d8a-4f28-97fe-13180e9eb0e5/constituents/11f3d570-ee2c-4cce-9dc7-2efbc38416d9"}