In some circumstances the upgrade to 3.0.0 from 2.7.0 fails with a NullPointerException, see e.g. SUPPORT-7639. It could get worked around by deleting the event index created by the 3.0.0 upgrade though with
But we need to investigate the actual cause, the NPE seems to be related to the `writeIndex` flag of the event index being null.
- 3.0.0 docs mention this known issue when upgrading sequentially from <=2.6.0 all the way up to 3.0.0
- this needs to get merged to master, latest and 3.0.0 branches
- the potential NPE on a write index flag missing is fixed in `UpdateIndexStep`, it just defaults to true in this case
- the `CreateIndexStep` uses the `ElasticSearchSchemaManager.createOptimizeIndex` method to create indexes