PDFViewer cannot scroll after dismiss other VC

My PDFViewer add the mail function for send mail to users. I am using the MFMailComposeViewController to do my mail. When I dismiss the mail view controller, then return to the PDFViewer. I scroll the viewer or thumbnail, the pdf image will disappear, only see the background color.
ps. ios 11 is work but under ios 11 is not work

Hi,

if you're using the demo implementation, remember to set b_outline to YES before showing a view over the reader; it prevents to close the reader on viewWillDisappear method of RDPDFViewController.