feat: add test for destroying empty component

test/runtime/samples/empty-component-destroy/Empty.svelte

@@ -0,0 +1,8 @@
+
+<script>
+	import { onMount } from 'svelte';
+
+	onMount(() => {
+		return () => console.log('destroy');
+	});
+</script>

test/runtime/samples/empty-component-destroy/_config.js

@@ -0,0 +1,17 @@
+export default {
+	html: `
+	  <button>destroy component</button>
+	`,
+
+	async test({ assert, target, window }) {
+		const button = target.querySelector('button');
+		const event = new window.MouseEvent('click');
+		const messages = [];
+		console.log = msg => messages.push(msg);
+		await button.dispatchEvent(event);
+		assert.htmlEqual(target.innerHTML, `
+			<button>destroy component</button>
+		`);
+		assert.deepEqual(messages, ['destroy']);
+	}
+};

test/runtime/samples/empty-component-destroy/main.svelte

@@ -0,0 +1,8 @@
+<script>
+	import Empty from './Empty.svelte';
+	let active = true;
+</script>
+
+<button on:click='{() => active = false }'>destroy component</button>
+
+<svelte:component this={active ? Empty : null} />