The audit event data requires that non-empty strings are passed in for event data points:

https://github.com/italiangrid/voms-admin-server/blob/a4c4d0bdcc5ffcb30765b1fd63bd3dc466c8af3c/voms-admin-server/src/main/java/org/glite/security/voms/admin/persistence/model/audit/AuditEventData.java#L48

However, the nullSafeCheck helper method does not handle empty strings correctly, so this can result in exceptions raised when adding a data point that contains an empty string value.

https://github.com/italiangrid/voms-admin-server/blob/0935532eb5b6447dbaf81f4af062c3474a0aac11/voms-admin-server/src/main/java/org/glite/security/voms/admin/event/auditing/NullHelper.java#L24

https://github.com/italiangrid/voms-admin-server/blob/a4c4d0bdcc5ffcb30765b1fd63bd3dc466c8af3c/voms-admin-server/src/main/java/org/glite/security/voms/admin/persistence/model/audit/AuditEvent.java#L117