Merge pull request #2731 from jekyll/doc-to_s

lib/jekyll/document.rb

@@ -246,7 +246,7 @@ module Jekyll
     #
     # Returns the content of the document
     def to_s
-      output || content
+      content || ''
     end
 
     # Compare this document against another document.

lib/jekyll/renderer.rb

@@ -49,14 +49,17 @@ module Jekyll
         output = render_liquid(output, payload, info)
       end
 
+      output = convert(output)
+      document.content = output
+
       if document.place_in_layout?
         place_in_layouts(
-          convert(output),
+          output,
           payload,
           info
         )
       else
-        convert(output)
+        output
       end
     end