fix 500 on project page after someone leave note on wall

app/views/projects/show.html.haml

@@ -5,9 +5,12 @@
       - if update.kind_of? Note
         %p
           %strong
+            - if update.target
               = update.target.class.name.titleize
               = truncate update.target.id.to_s, :length => 10
               commented
+            - else 
+              Project wall
           –
           = image_tag gravatar_icon(update.author_email), :class => "", :width => 16
           = truncate dashboard_feed_title(update), :length => 50