External QML drag and drop does not work on Windows touch screen devices.

QML external drag and drop does not work as expected when using touch input on Window Touch Screen devices.

The drop operation seems to get stuck on touch up and requires another touch down to reset the state.

Tested on: Windows 10 Lenvo Yoga 900

Steps to reproduce:

• Use a windows device that has a touch screen.
• Build and run the Qt example app externaldraganddrop.
• Using touch, drag items around in the test app.

I've also attached a video reproducing the issue using that demo app.