Error when adding book

### Problem

Adding a new book throws the following error(s).
```
athena.archive.org/0.gif?cache_bust=0.39113930530905083&server_ms=undefined&server_name=ol-web.us.archive.org&service=ol&kind=pageview&timediff=1&locale=en-GB&referrer=https%3A%2F%2Fopenlibrary.org%2Fbooks%2Fadd&loadtime=68&nav_to_done_ms=1084&iaprop_fontSize=25.6px&iaprop_devicePixelRatio=2.200000047683716&version=2&count=14:1


Failed to load resource: net::ERR_BLOCKED_BY_CLIENT
index.js:560 Possible Unhandled Promise Rejection: SyntaxError: "undefined" is not valid JSON
at JSON.parse ()
at 13127 (add-book.ed84720d4e1b3c08aa87.js:2:241)
at o (index.js:560:1)
at index.js:560:1
s._unhandledRejectionFn @ index.js:560
manifest.json:1 Manifest: Enctype should be set to either application/x-www-form-urlencoded or multipart/form-data. It currently defaults to application/x-www-form-urlencoded
add:1 Banner not shown: beforeinstallpromptevent.preventDefault() called. The page must call beforeinstallpromptevent.prompt() to show the banner.
```

### Reproducing the bug

1. Go to ...
2. Do ...

* Expected behavior:
* Actual behavior:

### Context

- Browser (Chrome, Safari, Firefox, etc): Brave
- OS (Windows, Mac, etc): Mac Sequoia 15.3.2 (24D81)
- Logged in (Y/N): y
- Environment (prod, dev, local): prod

### Breakdown

#### Requirements Checklist
* [ ]

#### Related files

*

#### Stakeholders

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