Fix empty lines in HTML

lib/repubmark/elems/footnote.rb

@@ -37,11 +37,10 @@ module Repubmark
               result += "</span>\n"
             end
           end
-          result += %(<a href="#{url}">#{link_text}</a>)
+          result += %(<a href="#{url}">#{link_text}</a>\n)
         else
-          result += link_text.to_s
+          result += "#{link_text}\n" if link_text
         end
-        result += "\n"
         result += @caption.to_html.to_s
         if alt_urls&.any?
           result += %[(#{