Federated Catalog is not loading, if there is a empty datasets

[KosrenDQ]

Bug Report

Describe the Bug

If the federated catalog endpoint of a connector is used and one of the queried catalogs does not have any asset, the datasets attribute in that catalog is missing, which leads to an endless loading screen.

Expected Behavior

The empty catalog will be skipped, and the overall federated catalog will be displayed.

Observed Behavior

Endless loading screen.

Steps to Reproduce

Steps to reproduce the behavior:

Provide a connector with an empty catalog.

Using this connector configuration:

{
  "connectorName": "tester",
  "managementUrl": "http://localhost:8080/api/management",
  "defaultUrl": "http://localhost:8080/api",
  "protocolUrl": "http://localhost:8080/api/v1/dsp",
  "federatedCatalogEnabled": true,
  "federatedCatalogUrl": "http://localhost:8080/api/catalog",
  "did": ""
}

1. Go to 'Catalog'
2. See error

Context Information

Used version: EDC v0.14.0

Possible Implementation

The catalog service should add a check to verify whether the datasets attribute exists before attempting to flatten it.