This is not only a CI error, but also a production error. See T255566#9134792 for the latest occurrence.
In an effort to resolve errors ending up in mw-error.log during a CI run in T249838: Fix WikibaseLexeme UnsupportedObjectExceptions in Wikibase CI builds, it was discovered that the tests LexemeEditEntityTest::testGivenInvalidDataInClearRequest_errorIsReported thows an UnsupportedObjectException if AbuseFilter is enabled that ends up in that file.
The exception logging for that test was temporarily disabled to clear the way for asserting that mw-error.log is empty during a CI run. However, we should still figure out why this happens in the first place and fix it properly.