Out-only deferred transition crashes when its outro is aborted from an $effect

Describe the bug

An out-only deferred transition crashes when an {#if} branch is removed and
then restored from an $effect during the same update.

Reproduction

<script>
	import { crossfade } from 'svelte/transition';

	let visible = $state(true);
	let restore = $state(false);
	const [send] = crossfade({});

	$effect(() => {
		if (restore) visible = true;
	});
</script>

<button
	onclick={() => {
		visible = false;
		restore = true;
	}}
>
	Reproduce
</button>

{#if visible}
	<p out:send={{ key: 'item' }}>Deferred outro</p>
{/if}

Deferred out transition reset crash #1

Deferred out transition reset crash #2

1. Open the browser console.
2. Click "Reproduce".

Actual behavior

Svelte throws:

TypeError: Cannot read properties of undefined (reading 'reset')

The stack contains:

• Object.reset
• Object.in
• resume_children

Expected behavior

The outro should be aborted and the branch should remain visible without a
runtime exception.

Additional information

The transition function intentionally returns another function, making it a
deferred transition. Restoring the branch from $effect happens before the
deferred transition facade initializes its internal animation.

The assignment inside $effect is intentional and is required to reproduce
the runtime race.

System Info

^5.57.0

Severity

annoyance