Upgrade fro 6.8.0 to 7.1.0 impossible

**Describe the bug**
We use the org.flowable:flowable-event-registry:7.1.0 dependency. We currently have version 6.8.0, DB schema also has the same version. We tried upgrading to 7.1.0, upgrade failed because flowable-event-registry-7.1.0.jar!/org/flowable/eventregistry/db/upgrade/flowable.all.upgradestep.7100.to.7101.eventregistry.sql tries to drop a table that does not exist.

**Expected behavior**
The upgrade happens without errors. The SQL command should contain IF EXISTS clause. Note: there still might be another problem, maybe the table should be present.