title: FB.AppRequest 0 objects are given message
body: <p>I'm trying to send a invitation with FB.AppRequest and i'm getting this error message:</p>
  
  <blockquote>
    <p>This action type requires 1 1 object but 0 0 objects are given.</p>
  </blockquote>
  
  <p>my request is made as follows.</p>
  
  <p><code>FB.AppRequest("Come play this great game!", InvitePlayersIds);</code></p>
  
  <p>This InvitePlayerIds is a collection with the player ids i've got through </p>
  
  <p><code>FB.API("/me/invitable_friends", HttpMethod.GET, InvitableFriendsCallback);</code></p>
  
  <p>Someone else had this problem?</p>