That error alone does not identify the root cause. Could you please share the complete stack trace, especially the deepest Caused by, along with your IIQ version and what action triggers the error?
The same Application.aggregationTypes error has occurred with different underlying causes. In one IIQ 8.3p4 case, SailPoint Support traced it to bad IDX values and the Correct IDX procedure resolved it. In another case, the underlying cause was a missing Schema object.
If your stack trace ends with a similar NullPointerException, I would then check the Correct IDX procedure. Its documented first execution runs the Support Task for Hibernate IDX in read mode without updating the database.