IBX-7055: Allowed to return `null` when content is not deleted #1411

Job	Run time
Unit tests & SQLite integration tests (7.4)	7m 9s
Run code style check (8.0)	2m 34s
Solr integration tests (7.4)	9m 59s
Unit tests & SQLite integration tests (8.0)	6m 43s
Solr integration tests (8.0)	9m 48s
Unit tests & SQLite integration tests (8.1)	7m 3s
Solr integration tests (8.1)	9m 43s
PostgreSQL integration tests (7.4)	24m 9s
MySQL integration tests (7.4)	12m 35s
PostgreSQL integration tests (8.0)	21m 9s
MySQL integration tests (8.0)	16m 53s
PostgreSQL integration tests (8.1)	18m 41s
MySQL integration tests (8.1)	12m 28s
	2h 38m 54s

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