fix: undefined document in worker

[patak-dev]

Fixes #12970

Description

Regression added by:

• feat: reuse existing style elements in dev #12678

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[patak-dev]

Bringing some notes we are discussing with @ArnaudBarre. Why this hasn't been an issue so far? I tested the repro at #12970, and if you do HMR you will get an error when checking for hasErrorOverlay:

client.ts:288 Uncaught (in promise) ReferenceError: document is not defined
    at hasErrorOverlay (client.ts:288:3)
    at handleMessage (client.ts:150:28)
    at WebSocket.<anonymous> (client.ts:91:5)

I tested with vite@4.0.0 and the issue is still there, so it isn't like we just started including the client in workers in the last minor. Folks may just cope with this error?
If you modify the main thread source code, it will HMR, the error appears but everything still works. If you modify the workers code, then it full-reloads so there is no error. In both cases the page is in a proper state, just with a noisy error in one case. @subframe7536 is this what you were experiencing before 4.3, no?

So we don't have HMR in workers AFAICS, we will full reload.

This PR isn't really fixing the real issue, but at least it patches things so previous apps can at least work. I think we should merge it as a temporal patch and maybe we should guard every document access in the worker.

[subframe7536]

yes, and this pr makes all work

[patak-dev]

Let's merge this one as a temporal patch. See more context at #12995