add missing gallery section

lib/philomena_web/controllers/stat_controller.ex

@@ -82,7 +82,13 @@ defmodule PhilomenaWeb.StatController do
 
   defp galleries do
     gallery_count = Repo.aggregate(Gallery, :count, :id)
-    gallery_size = Float.round(Repo.aggregate(Gallery, :avg, :image_count) || 0.0, 2)
+
+    gallery_size =
+      Repo.aggregate(Gallery, :avg, :image_count)
+      |> Kernel.||(Decimal.new(0))
+      |> Decimal.to_float()
+      |> trunc()
+
     distinct_creators =
       Gallery
       |> distinct(:creator_id)

lib/philomena_web/templates/stat/index.html.slime

@@ -75,6 +75,24 @@ elixir:
       = number_with_delimiter(@users_24h)
     ' have joined in the last 24 hours.
 
+  h3 Galleries
+  p
+    ' There are
+    span.stat>
+      = number_with_delimiter(@gallery_count)
+    ' existing image galleries on the site, created by
+    span.stat>
+      = number_with_delimiter(@distinct_creators)
+    ' distinct creators. There are, on average,
+    span.stat>
+      = number_with_delimiter(@gallery_size)
+    ' images in each gallery.
+  p
+    ' In total, images have been added to galleries
+    span.stat>
+      = number_with_delimiter(@images_in_galleries)
+    ' times.
+
   h3 Commissions
   p
     ' There are