Remove nils from season_download_rollups before sorting

Author: radical-ube

app/models/concerns/podcast_metrics.rb

@@ -62,8 +62,10 @@ def latest_season
 
   def season_download_rollups
     published_seasons.map do |season|
-      downloads_by_season(season_number: season).to_a.flatten
-    end.sort { |a, b| b[1] <=> a[1] }
+      downloads_by_season(season_number: season).to_a.flatten.presence
+    end
+      .compact
+      .sort { |a, b| b[1] <=> a[1] }
   end
 
   def season_label(season_number)