ios 中的缩略图关联？

Question

我正在尝试运行 cocoapod 依赖项ios-PDF-Reader，当我通过“文件”应用程序在手机上选择 pdf 时，出现以下错误：

[DocumentManager] Failed to associate thumbnails for picked URL file:///private/var/mobile/Containers/Data/Application/../../Welcome.pdf 
with the Inbox copy file:///private/var/mobile/Containers/Data/Application/../../tmp/com../Welcome.pdf: 
Error Domain=QLThumbnailErrorDomain Code=102 "(null)" 
UserInfo={NSUnderlyingError=0x28226cf90 {Error Domain=GSLibraryErrorDomain Code=3 "Generation not found" 
UserInfo={NSDescription=Generation not found}}}

以前有人遇到过无法关联缩略图错误吗？有没有简单的解决方法？这是它中断的代码：

extension TestPdfEpubViewController: UIDocumentPickerDelegate {
    func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
guard let selectedFileURL = urls.first else { return }
            //create pdf first
            let documentFileURL = Bundle.main.url(forResource: selectedFileURL.absoluteString, withExtension: "pdf")!
            let document = PDFDocument(url: documentFileURL)!
            //then display the pdf
            let readerController = PDFViewController.createNew(with: document)
            navigationController?.pushViewController(readerController, animated: true)
        }
}