fix destructuring test

test/runtime/samples/destructuring/main.html

@@ -2,6 +2,8 @@
 	import { createEventDispatcher } from 'svelte';
 
 	const dispatch = createEventDispatcher();
+
+	export let foo;
 </script>
 
 <button on:click='{() => dispatch("foo", { foo })}'>click me</button>