fixes #2311

app/models/dmail_filter.rb

@@ -1,6 +1,14 @@
 class DmailFilter < ActiveRecord::Base
   belongs_to :user
   attr_accessible :user_id, :words, :as => [:moderator, :janitor, :contributor, :gold, :member, :anonymous, :default, :builder, :admin]
+  validates_presence_of :user
+  before_validation :initialize_user
+
+  def initialize_user
+    unless user_id
+      self.user_id = CurrentUser.user.user_id
+    end
+  end
 
   def filtered?(dmail)
     dmail.from.level <= User::Levels::MODERATOR && (dmail.body =~ regexp || dmail.subject =~ regexp)