fix video rss

media.xml

@@ -51,7 +51,7 @@ layout: null
               {% endfor -%}
             <title>{% if video.persons and name_before_title -%}{{persons| strip}}: {% endif -%}{{video.title| xml_escape }}{% for conf in video.conferences -%}{% for c in site.conferences -%}{% if conf == c.acronym -%}{% if c.ecki -%}{{whitespace}}[{{c.title| xml_escape}}]{% endif -%}{% endif -%}{% endfor -%}{% endfor -%}{% if video.persons and name_after_title %}{{whitespace}}{{persons3| strip}}{% endif -%}</title>
             <description>{{ video.content | xml_escape }}</description>
-            <pubDate>{{ video.date | date_to_rfc822 }}</pubDate>
+            <pubDate>{{ video.release_date | date_to_rfc822 }}</pubDate>
             <link>{{ video.url | prepend: site.baseurl | prepend: site.url }}</link>
             <guid isPermaLink="true">{{ video.url | prepend: site.baseurl | prepend: site.url }}</guid>
           </item>