修改了一处bug

app/controllers/application_controller.rb

@@ -24,7 +24,7 @@ class ApplicationController < ActionController::Base
   end
 
   def current_user_is_author?(article)
-      @current_user.id == article.user_id
+    @current_user && @current_user.id == article.user_id
   end
 
   def current_user_can_star?(article)

app/views/articles/_comment_form.html.haml

@@ -22,4 +22,4 @@
       $(this).tab('show');
       preview('article_comment_content', 'preview');
     });
-  });
+  });