fix: prevent calling remove fn with null value in snippet_effect

[otodockal]

Closes #9678

There might be a bug related to snippet_effect or create_snippet_block fns...At some point block.d becomes [null] for some reason. Very likely not the right fix, just a hint.

• svelte 5.0.0-next.15
• @sveltejs/kit 1.27.6

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[trueadm]

Do you have a repro or example where this happens? That field should never become [null] so the fix is likely to be somewhere else. i.e. this line:

https://github.com/sveltejs/svelte/blob/main/packages/svelte/src/internal/client/render.js#L209

Is this creating [null] for you in your case?

[otodockal]

@trueadm you can reproduce the bug in this repo I've just created:
https://github.com/otodockal/svelte-5-runes-bug

Once you run it, try to navigate and the error is shown in the console.

When you remove this line (<Icon>→</Icon>), it will start working again.
https://github.com/otodockal/svelte-5-runes-bug/blob/main/src/routes/%2Bpage.svelte#L8

Is this creating [null] for you in your case?

I'll check it.