Summary

Background reindex is not supposed to fix the broken index. It shouldn't be possible to trigger it when the index is broken.

Steps to reproduce

1. Run Jira 7.12.3 with existing issues
2. Stop Jira
3. remove index files

   rm -rf <jirahome>/caches/indexes/
   

4. Start Jira
5. Go to "Jira indexing" administration page (<Jira_URL>/secure/admin/jira/IndexAdmin.jspa)

Expected result

Jira won't allow you to perform background reindex
In Jira 7.6.9 the screen looked like this:

Actual result

Jira will allow you to perform background reindex

Workaround

No workaround known