Updated Choices.js

Fixes scrollbar issue in IE11. There is an EDGE-CASE where-by if a user were to select the same option twice, the dropdown doesn't go away. This is, however a very extreme case and we are on the right track

src/scripts/choices.js

@@ -1386,7 +1386,7 @@ class Choices {
   _onMouseDown(event) {
     const { target, shiftKey } = event;
     // If we have our mouse down on the scrollbar and are on IE11...
-    if (target === this.choiceList && isIE11()) {
+    if (this.choiceList.element.contains(target) && isIE11()) {
       this._isScrollingOnIe = true;
     }