Only include email if author has an email address specified

feed.xml

@@ -32,7 +32,7 @@ sitemap: false
   <author>
     <name>{{ author.name }}</name>
     <uri>{{ site.url }}</uri>
-    <email>{{ author.email }}</email>
+    {% if author.email %}<email>{{ author.email }}</email>{% endif %}
   </author>
   <content type="html">{{ post.content | xml_escape }}
   &lt;p&gt;&lt;a href=&quot;{{ site.url }}{{ post.url }}&quot;&gt;{{ post.title }}&lt;/a&gt; was originally published by {{ author.name }} at &lt;a href=&quot;{{ site.url }}&quot;&gt;{{ site.title }}&lt;/a&gt; on {{ post.date | date: "%B %d, %Y" }}.&lt;/p&gt;</content>