title: UIDocumentPickerViewController crashes after picking documents
body: <p>I'm currently working on, macOs 10.15 beta 2, Xcode 11 beta 2, iPadOS 13 beta 2 (iPad Air 2),</p>
  
  <p>I have added UIDocumentPickerViewController as a child viewController in a tabview like this.</p>
  
  <pre><code>var controller : UIDocumentPickerViewController!
  func addDocumentPickerController() {
  
      controller = UIDocumentPickerViewController(
          documentTypes: ["public.png"], // choose your desired documents the user is allowed to select
          in: .import // choose your desired UIDocumentPickerMode
      )
      controller.delegate = self
      controller.hidesBottomBarWhenPushed = true
      controller.allowsMultipleSelection = true
  
      self.view.addSubview(controller.view)
      let window = UIApplication.shared.keyWindow
      let topPadding = window?.safeAreaInsets.top
  
      self.controller.view.snp.makeConstraints { (make) in
          make.leading.equalToSuperview()
          make.trailing.equalToSuperview()
          make.top.equalTo(topPadding ?? 0)
          make.bottom.equalToSuperview()
      }
  }
  </code></pre>
  
  <p>Now in delegates</p>
  
  <pre><code>func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
  }
  </code></pre>
  
  <p>this methods doesn't get called.</p>
  
  <p>Only below error in console.</p>
  
  <pre><code>[TraitCollection] Class _UIRootPresentationController overrides the -traitCollection getter, which is not supported. If you're trying to override traits, you must use the appropriate API.
  [TraitCollection] Class UIPopoverPresentationController overrides the -traitCollection getter, which is not supported. If you're trying to override traits, you must use the appropriate API.
  [TraitCollection] Class _UISheetPresentationController overrides the -traitCollection getter, which is not supported. If you're trying to override traits, you must use the appropriate API.
  [TraitCollection] Class UIPreviewPresentationController overrides the -traitCollection getter, which is not supported. If you're trying to override traits, you must use the appropriate API.
  [DocumentManager] The view service did terminate with error: Error Domain=_UIViewServiceInterfaceErrorDomain Code=3 "(null)" UserInfo={Message=Service Connection Interrupted}
  [DocumentManager] Remote view controller crashed with error: Error Domain=_UIViewServiceInterfaceErrorDomain Code=3 "(null)" UserInfo={Message=Service Connection Interrupted}. Trying to relaunch.
  </code></pre>
  
  <p>Any idea on this is happening. </p>