fix: reworking some code smell issues

lib/bds/ui/dashboard.ex

@@ -194,5 +194,5 @@ defmodule BDS.UI.Dashboard do
     if blank?(post.title), do: post.slug || "", else: post.title
   end
 
-  defp blank?(value), do: value in [nil, ""]
+  defp blank?(value), do: BDS.Values.blank?(value)
 end

lib/bds/ui/sidebar.ex

@@ -1125,5 +1125,5 @@ defmodule BDS.UI.Sidebar do
 
   defp media_size_label(_size), do: "0 B"
 
-  defp present?(value), do: value not in [nil, ""]
+  defp present?(value), do: BDS.Values.present?(value)
 end