Unable to add child in tree view of doctype "Item Group"

Description of the issue

“Add Child” is not working in the tree view of doctype “Item Group”, when I set the field “taxes” as mandatory.

Context information (for bug reports)

Output of bench version

erpnext 13.x.x-develop
frappe 13.x.x-develop

Steps to reproduce the issue

  1. Open doctype “item group” under developer mode
  2. Set field “taxes” as mandatory.
  3. Go to Item group tree view and hit the “add child” button

Observed result

nothing happen

Expected result

popup dialog for entering information of new child

Stacktrace / full error message

grid.js:440 Uncaught TypeError: Cannot read property 'forEach' of undefined
    at Grid.setup_fields (grid.js:440)
    at Grid.refresh (grid.js:286)
    at ControlTable.refresh_input (table.js:112)
    at ControlTable.refresh (base_control.js:102)
    at Dialog.attach_doc_and_docfields (layout.js:329)
    at Dialog.refresh (layout.js:237)
    at Dialog.make (field_group.js:23)
    at Dialog.make (dialog.js:53)
    at new Dialog (dialog.js:18)
    at TreeView.new_node (treeview.js:283)

Additional information

ERPNext: v13.x.x-develop () (develop)
Frappe Framework: v13.x.x-develop () (develop)