when ext-grid enabled, it has error when the tree is empty

[yangjuncode]

the error is:

TypeError: node is undefined

the normal tree without ext-grid is fine with empty source

    $("#old-tree").fancytree({
      checkbox: true,
      source: [],

  })

Environment

• Browser type and version:firefox 70
• jQuery and jQuery UI versions:jQuery UI 1.12.1, jQuery 3.4.1
• Fancytree version:2.33.0
  enabled/affected extensions: ext-grid

[yangjuncode]

this is my modified demo file

sample-3rd-grid-scrollbar.html.zip

[mar10]

Thanks for reporting!