[fix] allow missing routes folder

[dummdidumm]

Fixes #6921

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🦋 Changeset detected

Latest commit: cf82821

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@sveltejs/kit	Patch

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[dummdidumm]

GitHub diff fucks this up - nothing changed here except moving the error message into the if block, the rest is just indentation difference

[Rich-Harris]

errr i guess i rescind my approval until the tests pass 😅

[dummdidumm]

The test shows that nodes for the root layout and error are created. This means that the running code later on can safely assume these to be always present. Before that, the manifest was generated without these, causing dev and build to fail with "cannot read properties of nodes[0].component" or sth like that. Adding the default nodes even in case of a missing routes folder seems like the better option, even if it seems somewhat strange at first. I'll add a comment to the manifest about this.