back out r8124

r8124 shows ":roles can't be empty".

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@8125 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/member.rb

@@ -84,7 +84,7 @@ class Member < ActiveRecord::Base
   protected
 
   def validate_role
-    errors.add_on_empty :roles if member_roles.empty? && roles.empty?
+    errors.add_on_empty :role if member_roles.empty? && roles.empty?
   end
 
   private