destroying idb instance and then replicating find index results in idb blocked event

### Issue
Sometimes in my app I need to destroy my database before replicating. (If I don't need to do this, I would be happy to learn a workaround, but it seems that if I recreate the server DB, the replication won't load the new changes.) When I replicated after adding a find index, I got an error log "this should never happen" due to an IndexedDB blocked event.

### Info
- Environment: Browser
- Platform: Chrome
- Adapter: indexeddb
- Server: PouchDB Server

### Reproduce
https://github.com/Eduardogbg/pouch-idb-blocked