Error: The requested resource isn't a valid image for ...

When deploy `NextjsGlobalContainers` or `NextjsRegionalContainers`, image optimization is resulting in this error on server: `⨯ The requested resource isn't a valid image for /static/alexander-andrews-brAkTCdnhW8-unsplash.jpg received text/html; charset=utf-8`

It's not a permission issue because
```
Output: Image file is readable
Command: cat /mnt/cdk-nextjs/public/static/alexander-andrews-brAkTCdnhW8-unsplash.jpg > /dev/null && echo "Image file is readable" || echo "Cannot read image file"
```

packages/next/src/server/image-optimizer.ts
```
if (!upstreamType.startsWith('image/') || upstreamType.includes(',')) {
if (!opts.silent) {
Log.error(
"The requested resource isn't a valid image for",
href,
'received',
upstreamType
)
}
throw new ImageError(400, "The requested resource isn't a valid image.")
}
```

Need to debug in packages/next/src/server/lib/router-server.ts line 320 (`const handleRequest = async (handleIndex: number) => {`) to see why it's failing to read

Begin with packages/next/src/server/image-optimizer.ts and packages/next/src/server/lib/router-server.ts around line 320, then reproduce the failure in NextjsGlobalContainers or NextjsRegionalContainers using the reported image. Done means image optimization no longer receives text/html for a readable image and the deployment succeeds.

Written by the indexing model from the issue text.