using blank instead of checking for nil, since mongo import make these bank

app/models/invitation.rb

@@ -57,7 +57,7 @@ class Invitation < ActiveRecord::Base
     invitee.invites = opts[:invites] || 5
     if invitee.new_record?
       invitee.errors.clear
-      invitee.serialized_private_key ||= User.generate_key
+      invitee.serialized_private_key = User.generate_key if invitee.serialized_private_key.blank?
       invitee.send(:generate_invitation_token)
     elsif invitee.invitation_token.nil?
       return invitee

app/models/user.rb

@@ -260,7 +260,7 @@ class User < ActiveRecord::Base
     self.person.url = AppConfig[:pod_url]
 
 
-    self.serialized_private_key ||= User.generate_key
+    self.serialized_private_key = User.generate_key if self.serialized_private_key.blank?
     self.person.serialized_public_key = OpenSSL::PKey::RSA.new(self.serialized_private_key).public_key
 
     self