fix: fix merge style func

[azat-io]

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🦋 Changeset detected

Latest commit: db8bea7

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[Conduitry]

What is this fixing?

[azat-io]

I had a problem when using the Shiki Magic Move package (https://github.com/shikijs/shiki-magic-move/blob/main/src/svelte/ShikiMagicMoveRenderer.svelte).

In the style attribute on the first render comes undefined. That's the reason I'm getting the error:

Cannot read properties of undefined (reading 'split')

[Rich-Harris]

Are you able to add a test (or reproduce the bug in https://svelte-5-preview.vercel.app/)?

[Rich-Harris]

Ah this seems to be enough to reproduce it, but only in SSR (so not in the REPL)

<span style:color="red" style={null}>test</span>

[Rich-Harris]

thanks!