Errors from within +layout.js are not being caught and passed to +error

[bdanoit]

Describe the bug

Errors thrown from within +layout.js are not being caught and passed to +error.svelte

If I throw the error from +page.js it is being caught and passed to +error.svelte

Reproduction

https://stackblitz.com/edit/sveltejs-kit-template-default-f1qmuw?file=README.md

Logs

No response

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (4) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 16.14.2 - /usr/local/bin/node
    Yarn: 1.22.10 - /bin/yarn
    npm: 7.17.0 - /bin/npm
  npmPackages:
    @sveltejs/adapter-auto: next => 1.0.0-next.64 
    @sveltejs/kit: next => 1.0.0-next.418 
    svelte: ^3.46.0 => 3.49.0 
    vite: ^3.0.0 => 3.0.8

Severity

serious, but I can work around it

Additional Information

No response

[Conduitry]

Sounds like a duplicate of #3068. It's not immediately apparent what should happen when your top-level layout load throws an error, since that data is needed to render that layout, which is needed to render that top-level +error.page