Cover fallback processing for IA identifiers doesn't work

## Description
> What problem are we solving? What does the experience look like today? What are the symptoms?

When I load up a new instance of openlibrary, I'm seeing badly formatted URIs for the default covers like so:


When I edit
openlibrary/templates/books/custom_carousel.html
and add $_(book)

I see:
```
], 'ia': ['completeworksofm01twaiiala', 'completeworksofm21twai', 'completeworksofm00twai', 'completeworksofm10twai'], 'author_key': ['OL18319A'], 'read_url': '//archive.org/stream/completeworksofm01twaiiala'}>
```

## Expectation
A book should only ever have one ia so why it has an aray I'm not sure.
An issue with solr that powers this carousel or with the initial data maybe (#1846)?
Maybe this is a bug and the template is wrong and for some reason this doesn't show up in production?

## Details