fix bug for https://github.com/RubaXa/Sortable/issues/628

Sortable.js

@@ -23,7 +23,7 @@
 	}
 })(function () {
 	"use strict";
-	
+
 	if (typeof window == "undefined" || typeof window.document == "undefined") {
 		return function() {
 			throw new Error( "Sortable.js requires a window with a document" );
@@ -335,7 +335,7 @@
 					_this._disableDelayedDrag();
 
 					// Make the element draggable
-					dragEl.draggable = true;
+					dragEl.draggable = _this.nativeDraggable;
 
 					// Chosen item
 					_toggleClass(dragEl, _this.options.chosenClass, true);