CacheBackedLuceneSearchMapperRegistry isn't updated on plugin events in 5.9.1-beta4

The CacheBackedLuceneSearchMapperRegistry is supposed to be updated whenever a plugin event occurs.

However this is not working in Confluence 5.9.1-beta4 because the searchMapperRegistry field in LuceneSearchMapperRegistryCacheUpdateListener is always null (probably due to autowiring issues).

The effect of this behaviour is that the LuceneSearchManager can only use mappers provided by plugins that were already enabled before the first search request is being processed (because the cache inside CacheBackedLuceneSearchMapperRegistry is filled on first request).

Mappers provided by plugins installed later on are not visible until Confluence is restarted.

This causes several key features of the Scroll Versions plugin to break, therefore I'm setting the priority to 'Critical'.
Please let us know if you require a 5.9 compatible pre-release version of Scroll Versions for testing. The versions currently available on the market place are not yet compatible with 5.9.*.