fix referrer cascade to really update referencing document

not having those lead to an error because the property "name" was an empty string. and the reference field was not updated.

i really don't understand why CascadePersistTest::testCascadeManagedDocumentReferrerDuringFlush does not fail but it did fail in our project. this change breaks no test and makes our project work. if somebody has an idea how to write a test that shows something was wrong and is now fixed, please tell.