Send a Facebook iOS request without requiring web dialog login

Question

In my iOS app, I have a user logged in via fast app switch and the native iOS app. When i open a request dialog via

NSMutableDictionary* params =   
[NSMutableDictionary dictionaryWithObjectsAndKeys: @"<my_app_id>", @"app_id", friendID, @"to", nil ];

[FBWebDialogs presentRequestsDialogModallyWithSession:[FBSession activeSession]
                                              message:[NSString stringWithFormat:@"This is a facebook invite"]
                                                title:@"Hello!"
                                           parameters:params
                                              handler:^(FBWebDialogResult result, NSURL *resultURL, NSError *error) { } ];

the app opens a web dialog which doesn't seem to have session data, so it requires a login. I assume this is because the webview doesn't have the session data gained when the user signed in via the native iOS app.

I'm wondering if there's a way to either show the requests dialog from the native app, or to ensure that the logged in session is used for the web dialog so that the user isn't required to login again?

Thanks!