Code for managing a missing home page is broken

[joelanman]

Description of the issue

If /app/views/index.html is missing, the kit crashes with error:

node:internal/fs/promises:639
  return new FileHandle(await PromisePrototypeThen(
                        ^

Error: ENOENT: no such file or directory, open '/Users/joe.lanman/prototypes/dds/node_modules/govuk-prototype-kit/prototype-starter/app/views/index.njk'
    at async open (node:internal/fs/promises:639:25)
    at async Object.readFile (node:internal/fs/promises:1242:14)
    at async /Users/joe.lanman/prototypes/dds/node_modules/govuk-prototype-kit/server.js:172:31 {
  errno: -2,
  code: 'ENOENT',
  syscall: 'open',
  path: '/Users/joe.lanman/prototypes/dds/node_modules/govuk-prototype-kit/prototype-starter/app/views/index.njk'
}

If other pages are missing, the kit handles it correctly with the 404 page.

I think this was introduced in this PR which was supposed to render a home page even if one was missing.

• Homepage #1593