404 check before trying to grab the current file

[ccorda]

closes #244.

Before, we had this:

curl -I https://bubsnext.wpengine.com/foo
HTTP/2 307 
server: nginx
date: Thu, 09 Feb 2023 23:15:24 GMT
content-type: text/html; charset=UTF-8
content-length: 0
location: https://bubs-next-git-sitemaps-robots-patronage.vercel.app/posts/kitchen/
x-powered-by: WP Engine
link: <https://bubsnext.wpengine.com/wp-json/>; rel="https://api.w.org/"
expires: Wed, 11 Jan 1984 05:00:00 GMT
x-redirect-by: WordPress
x-cacheable: non200
cache-control: max-age=600, must-revalidate
x-cache: HIT: 1
x-cache-group: normal
x-orig-cache-control: no-cache, must-revalidate, max-age=0

Now (I deployed to live site for testing), we get this:

HTTP/2 307 
server: nginx
date: Thu, 09 Feb 2023 23:43:15 GMT
content-type: text/html; charset=UTF-8
content-length: 0
location: https://bubs-next-git-sitemaps-robots-patronage.vercel.app/foo
x-powered-by: WP Engine
link: <https://bubsnext.wpengine.com/wp-json/>; rel="https://api.w.org/"
expires: Wed, 11 Jan 1984 05:00:00 GMT
x-redirect-by: WordPress
x-cacheable: non200
cache-control: max-age=600, must-revalidate
x-cache: MISS
x-cache-group: normal
x-orig-cache-control: no-cache, must-revalidate, max-age=0

[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

1 Ignored Deployment

| Name | Status | Preview | Updated | | :--- | :----- | :------ | :------ | | **bubs-next** | ⬜️ Ignored ([Inspect](https://vercel.com/patronage/bubs-next/ChEM9yToSF1HLDRFDBDtNLDXFuCZ)) | | Feb 9, 2023 at 11:43PM (UTC) |