fix(examples): hide "undefined" domain in HN example (#4643)

* fix(examples): hide "undefined" domain in HN example

This commit introduces a null-undefined check against the domain of the HN items in the Hacker News example.

* Update site/content/examples/21-miscellaneous/01-hacker-news/Item.svelte

Co-Authored-By: Antony Jones <ant@enzy.org>

Co-authored-by: Antony Jones <ant@enzy.org>

site/content/examples/21-miscellaneous/01-hacker-news/Item.svelte

@@ -28,7 +28,9 @@
 <article>
 	<a href="{url}">
 		<h1>{item.title}</h1>
+		{#if item.domain}
 			<small>{item.domain}</small>
+		{/if}
 	</a>
 
 	<p class="meta">submitted by {item.user} {item.time_ago}