Customization dialog for top panel bug: prevents customizing

Customization dialog for top panel bug: prevents customizing

Workspace or Wiki > Settings > Customization > Top panel > Edit button

Should invoke dialog for editing top panel.

That panel does get invoked (as judged by DOM inspector), but it's positioned below bottom of browser window. Cannot be brought on screen by editing DOM.

Might be due to this error that appears in console:

18:17:54.853 TypeError: Argument 1 of Node.appendChild is not an object.
showDialogBox() wikisetting.js:1
showURLInDialogBox/<() wikisetting.js:1
$1/xmlhttp.onreadystatechange() wikisetting.js:8
1 wikisetting.js:1:2560

Effect: can't edit top panel of Wiki or Workspace.

My issue tracking Id:  GWZ1033