feat: {@html} should handle null and undefined as empty string

[adiguba]

Fix #13069 {@html} should handle null and undefined as empty string

Note : I edited from github, so no test/lint :(

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[changeset-bot]

🦋 Changeset detected

Latest commit: d420920

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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[Rich-Harris]

thank you!

[Rich-Harris]

uh wow looks like i broke a whole bunch of tests by tweaking the test logic. am about to get on a plane so if i can't fix it in the next five minutes, someone feel free to take over

[Rich-Harris]

hmm. it seems that undefined and null are already rendered literally in Svelte 4 (that accounts for at least one of the test failures) so this is technically a breaking change — I think it's probably a sensible one (since it mirrors the behaviour of {nullish}) but would like a second opinion from maintainers!

[trueadm]

This is good and we have documented this breaking change in other areas so it makes sense here too.

[trueadm]

For some reason I don't have permissions to push to this PR. So I had to make a follow up PR #13092