title: iOS: Javascript code in WKWebView got “query cancelled” error after selecting photo from photo library and before uploading to the server
body: <p>I use Xcode 9.1(9B55), iOS 11.1 both simulator and real iPhone/iPad.</p>
  
  <p>The website(HTML5+Javascript) I used in mobile safari acts perfectly. But in my iOS app(Objective-C), which uses WKWebView to access the same web page, and set all the "privacy - Photo Library Usage" and others, always got the error below after selecting photo from photo library and before uploading to the server:</p>
  
  <p>[discovery] errors encountered while discovering extensions: Error Domain=PlugInKit Code=13 "query cancelled" UserInfo={NSLocalizedDescription=query cancelled}</p>
  
  <p>But something strange was that I had a successful run for just one time.</p>
  
  <p>I've several threads about this issue, but have no clear solution. Someone said it's a bug of iOS 11.x, but I've tried it on iOS 9.x, the error was same.</p>