TypeError: this._items[(this._items.length - 1)] is undefined

[jtpio]

Getting the following logged in the dev tools console while trying the latest version from main on Binder: https://mybinder.org/v2/gh/jupyter/notebook/main?urlpath=tree

TypeError: this._items[(this._items.length - 1)] is undefined
    _panelChildHook webpack://_JUPYTERLAB.CORE_OUTPUT/../packages/application/lib/panelhandler.js?:42
    invokeHook webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/messaging/dist/index.es6.js?:391
    passed webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/messaging/dist/index.es6.js?:150
    every webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/algorithm/dist/index.es6.js?:1883
    sendMessage webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/messaging/dist/index.es6.js?:149
    set parent webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/widgets/dist/index.es6.js?:990
    insertWidget webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/widgets/dist/index.es6.js?:2525
    addWidget webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/widgets/dist/index.es6.js?:2505
    addWidget webpack://_JUPYTERLAB.CORE_OUTPUT/../node_modules/@lumino/widgets/dist/index.es6.js?:3608
    SidePanelHandler webpack://_JUPYTERLAB.CORE_OUTPUT/../packages/application/lib/panelhandler.js?:110
    NotebookShell webpack://_JUPYTERLAB.CORE_OUTPUT/../packages/application/lib/shell.js?:41
    NotebookApp webpack://_JUPYTERLAB.CORE_OUTPUT/../packages/application/lib/app.js?:36
    main webpack://_JUPYTERLAB.CORE_OUTPUT/./build/index.js?:358