I'm creating this new issue from an error report added recently to HHH-12338, which nobody seemed to notice.
The fix applied for causes a regression when @ElementCollection and @CollectionTable is used. The following mapping taken from an entity used to work until Hibernate 5.2.16. It causes a NPE for criteria queries starting from 5.2.17.
Until 5.2.16, the JPA meta model class generated for this entity contains a SetAttribute for readers:
Using 5.2.17, this becomes a SingularAttribute instead, which is obviously wrong (and it seems that @ElementCollection is not taken into account).
As a result, the following code then throws a NPE when creating a fetch join (last line). Debugging showed that Doc_.readers is null.
Observed with both Wildfly 10.1 and 12.