Gustavo Fernandes Thank you for this report!

ExtendedSearchIntegrator is part of an implementation package and as such, should not be accessed by user nor service-provider code. Your snippet of code is, in theory, unsupported, since it's making use of ExtendedSearchIntegrator.
If you want to execute this query, you should take advantage of org.hibernate.search.FullTextSession.createFullTextQuery(QueryDescriptor, Class<?>...). You'll have to provide the targeted entities once again, though.

This should incidentally solve the NPE issue. Can you please confirm this?

Now, I agree there still is an issue somewhere, but I think it's more of an API problem here. I have created HSEARCH-2369 Open , HSEARCH-2370 Open and HSEARCH-2371 Open to address those issues.