fix(cc-network-group-dashboard): prevent error when 404

Since the `@clevercloud/client` package returns `null` instead of 
throwing when facing a `404` response, we need to make sure the code 
stops after setting the component state to `error` if data is null

Author: florian-sanders-cc

src/components/cc-network-group-dashboard/cc-network-group-dashboard.smart.js

@@ -35,6 +35,7 @@ defineSmartComponent({
       .then((ng) => {
         if (ng == null) {
           updateComponent('state', { type: 'error' });
+          return;
         }
 
         updateComponent('state', {