No renumbering if content is empty

app/helpers/digest_helper.rb

@@ -3,6 +3,7 @@ module DigestHelper
   # Important mechanism, to ensure the digest will not have the same footnote
   # link multiple times
   def renumber_footnotes(id, description)
+    return if description.nil? || description.blank?
     description.gsub(/\[(\d)+\]/, "[#{id}_\\1]")
   end
 end