Judge whether the node is the sibling nodes's last node.
If you use the 'exhide' pack, so this attribute will only support the node which be shown.
Do not initialize or modify it, it is created by the zTree.
true means: the node is last node.
false means: the node is not last node.
If the node has been hidden, isLastNode = false
var treeObj = $.fn.zTree.getZTreeObj("tree");
var sNodes = treeObj.getSelectedNodes();
if (sNodes.length > 0) {
var isLastNode = sNodes[0].isLastNode;
}