Bug fix for issue lukasoppermann#424

Disclaimer: I am only playing with this for an hour or so.
But I do think that I just fixed no less than three issues: lukasoppermann#424 and two issues that appear to be the same (@278 and lukasoppermann#163).
But I tested on only one machine.

src/html5sortable.ts

@@ -421,6 +421,7 @@ export default function sortable (sortableElements, options: configuration|objec
 
       dragging.classList.remove(options.draggingClass)
       attr(dragging, 'aria-grabbed', 'false')
+      dragging.style.display = ""
 
       if (dragging.getAttribute('aria-copied') === 'true' && data(dragging, 'dropped') !== 'true') {
         dragging.remove()