alr detects that the index is not loadable and errs out, which in turn prevents using alr index --del to remove the offending index.

The current solution is to manually delete the index metadata folder from the alr config folder, which is not obvious to the user.

Alternatives:

1. Give a warning instead of erroring. Probably not desirable, since alr is then operating in an incomplete environment according to what the user configured.
2. Indicate in the error message the folder to be manually deleted. May be good enough, since the reason for the bad situation is that the user has removed the index contents externally, so a degree of manual intervention has happened and can be reasonably asked for again.