Warning: array_unshift() [function.array-unshift]:

I am getting the following warning Conditions- Role user selectable and when administrator create user we have the choice to select the roles 1 Usual Administrator page selection check boxes and also AAR drop down box to select role.
If we set the AAR settings as not required and try yo create a user through normal user creation we get the following error

Warning: array_unshift() [function.array-unshift]: The first argument should be an array in autoassignrole_form_user_register_form_alter() (line 136 of E:\wamp\www\sites\all\modules\autoassignrole\autoassignrole.module).