Uncaught TypeError: Cannot read properties of undefined (reading 'children')

[lin onetwo]

            var l = function() {
                    var r = $tw.wiki.getTiddler("$:/StoryList");
                    if (r && r.fields.list.length) {
                        var l = null;
                        var o = Number.MAX_VALUE;
                        var f = i.children;
                        var u = t.classNames.tiddlerFrame;

var f = i.children; // here

When opening wiki whth calendar layout opened.

[lin onetwo]

Uncaught TypeError: Cannot read properties of undefined (reading 'children')
at l (hotzone.js:10:1068)
at eval (hotzone.js:10:1521)