When an empty Object State Group is present in the system the indexing does not index any Content (when using Solr) or fails with an error (Elastic).

Setup:
Configure ElasticSearch or Solr

Steps to reproduce:
1. Login as admin
2. Go to Admin -> Object States
3. Create a new Object State Group with name Test and identifier Test
4. Run php bin/console ezplatform:reindex

Expected:
Indexing works as expected - Content Items are indexed

Actual:
ElasticSearch:
Error is thrown:

In Handler.php line 143:

  Cannot traverse an already closed generator

Solr:
No error is thrown, but no items are indexed.