[Vapor] fallback slot content not rendered if content is comment

[alex-snezhko]

Vue version

3.6.0-alpha.2

Link to minimal reproduction

https://play.vuejs.org/#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

Steps to reproduce

Observe that in initial state (vapor mode active), the comment is considered as the content of the slot.

If vapor is removed from the components, the comment is not considered and the fallback content is rendered.

What is expected?

A slot content containing only comments should trigger the fallback content to render.

What is actually happening?

The comment is considered as the slot content in vapor mode, resulting in the fallback not being rendered.

System Info

Any additional comments?

No response