错误消息fbcdn.net不允许使用网址

Question

我试图用这段代码分享帖子：

// Put together the dialog parameters
    NSMutableDictionary *params = [[NSMutableDictionary alloc]init];
    [params setValue:[Campaign sharedInstance].name forKey:@"name" ];
    [params setValue:@"desription" forKey:@"description"];
    [params setValue:picture.facebookPicture.link forKey:@"link"];
    [params setValue:picture.facebookPicture.source forKey:@"picture"];

    // Show the feed dialog
    [FBWebDialogs presentFeedDialogModallyWithSession:nil                                             parameters:params handler:^(FBWebDialogResult result, NSURL *resultURL, NSError *error) {
        if(error) {
            [basicViewController toastMessage:[@"Error sharing on Facebook: " stringByAppendingString:error.localizedDescription]];
        }}];

我收到错误，因为图片的来源是来自facebook。 我该怎么做才能添加想要的Facebook图片并仍然使用fbwebdialogs？