Fixed: TypeError in WikiController#destroy_attachment (#1281).

git-svn-id: http://redmine.rubyforge.org/svn/trunk@1444 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/attachment.rb

@@ -68,9 +68,7 @@ class Attachment < ActiveRecord::Base
 
   # Deletes file on the disk
   def after_destroy
-    if self.filename?
-      File.delete(diskfile) if File.exist?(diskfile)
-    end
+    File.delete(diskfile) if !filename.blank? && File.exist?(diskfile)
   end
 
   # Returns file's location on disk