Bind aggregates over scoped tags to their subtree

CccConventions::TAG_SCOPES maps "update" and "pressemitteilung" to /updates
and "disclosure" to /disclosure. Page.aggregate applies the mapping, so an
aggregate over one of those tags is bounded by its subtree regardless of what
the shortcode says. Tags stay unrestricted; positions are publish-gated.

Both RSS actions call Page.aggregate rather than repeating its tag join.

Empty feeds no longer crash: Atom falls back to the current time for the
required <updated>, and the optional dc:date is omitted.

1 files changed, 1 insertions, 1 deletions

diff --git a/app/views/rss/updates.rdf.builder b/app/views/rss/updates.rdf.builder
index b02d34ff..b4fecdb0 100644
--- a/app/views/rss/updates.rdf.builder
+++ b/app/views/rss/updates.rdf.builder
@@ -6,7 +6,7 @@ xml.tag!("rdf:RDF", "xmlns:rdf" => "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xml.title("Chaos Computer Club: Updates")
     xml.link("https://www.ccc.de")
     xml.description("Kabelsalat ist gesund.")
-    xml.tag!("dc:date", @items.first.published_at.xmlschema)
+    xml.tag!("dc:date", @items.first&.published_at&.xmlschema) if @items.any?
   end
 
   xml.image( "rdf:about" => "https://www.ccc.de/images/chaosknoten.gif") do