Fix custom emojis not detected when used in content warning (#5049)

app/lib/formatter.rb

@@ -63,6 +63,12 @@ class Formatter
     Sanitize.fragment(html, config)
   end
 
+  def format_spoiler(status)
+    html = encode(status.spoiler_text)
+    html = encode_custom_emojis(html, status.emojis)
+    html.html_safe # rubocop:disable Rails/OutputSafety
+  end
+
   private
 
   def encode(html)