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Drag and drop does not work in Firefox

See original GitHub issue

When I am trying to run example from https://amsik.github.io/liquor-tree/#Drag-amp-Drop in Firefox v63.0 on Windows I am getting following error in browser console:

Start dragging: MVVM Pattern dark:74:12
TypeError: n is undefined liquor-tree:formatted:1393

The undefined n refers to this line

for (var t, n = e.path, i = 0; i < n.length; i++) if (t = n[i].className || '', /tree-node/.test(t)) return n[i];

in following method:

initDragListeners: function () {
  var e,
  t = this,
  n = function () {
    window.removeEventListener('mouseup', i, !0),
    window.removeEventListener('mousemove', r, !0)
  },
  i = function (i) {
    t.$$startDragPosition || i.stopPropagation(),
    t.draggableNode && t.draggableNode.node.state('dragging', !1),
    t.$$dropDestination && t.tree.isNode(t.$$dropDestination) && (O(t.$$dropDestination.vm.$el, null), t.draggableNode.node.finishDragging(t.$$dropDestination, e), t.$$dropDestination = null),
    t.$$possibleDragNode = null,
    t.$set(t, 'draggableNode', null),
    n()
  },
  r = function (i) {
    if (!t.$$startDragPosition || (r = i, o = t.$$startDragPosition, Math.abs(r.clientX - o[0]) > 5 || Math.abs(r.clientY - o[1]) > 5)) {
      var r,
      o;
      if (t.$$startDragPosition = null, t.$$possibleDragNode) {
        if (!1 === t.$$possibleDragNode.startDragging()) return n(),
        void (t.$$possibleDragNode = null);
        t.$set(t, 'draggableNode', {
          node: t.$$possibleDragNode,
          left: 0,
          top: 0
        }),
        t.$$possibleDragNode = null
      }
      t.draggableNode.left = i.clientX,
      t.draggableNode.top = i.clientY;
      var s = function (e) {
        var t = function (e) {
          for (var t, n = e.path, i = 0; i < n.length; i++) if (t = n[i].className || '', /tree-node/.test(t)) return n[i];
          return null
        }(e);
        return t || null
      }(i);
      if (t.$$dropDestination && O(t.$$dropDestination.vm.$el, null), s) {
        var a = s.getAttribute('data-id');
        if (t.draggableNode.node.id === a) return;
        if (!t.$$dropDestination || t.$$dropDestination.id !== a) {
          t.$$dropDestination = t.tree.getNodeById(a);
          var d = T([t.draggableNode.node,
          t.$$dropDestination], t.tree.options.dnd, 'onDragFinish');
          if (!t.$$dropDestination.isDropable() || !1 === d) return void (t.$$dropDestination = null)
        }
        e = function (e, t) {
          var n = t.getBoundingClientRect(),
          i = n.height / 3,
          r = _.ON;
          return n.top + i >= e.clientY ? r = _.ABOVE : n.top + 2 * i <= e.clientY && (r = _.BELOW),
          O(t, r),
          r
        }(i, s)
      }
    }
  };
  window.addEventListener('mouseup', i, !0),
  window.addEventListener('mousemove', r, !0)
}

In Chrome it works properly.