如果我关闭我的扩展
[self.extensionContext cancelRequestWithError:error];
错误不会通过完成块返回给应用程序UIActivityViewController
activityError
[vc setCompletionWithItemsHandler:^(NSString *activityType, BOOL completed, NSArray *returnedItems, NSError *activityError) {
// activityError is nil, even when cancelRequestWithError: called with error
}