Bug report

Grid with ColumnMenu groups in combination with multi-column headers gives an error:

kendo.all.js:326079 Uncaught TypeError: Cannot read properties of undefined (reading 'length')

Reproduction of the problem
Dojo: https://dojo.telerik.com/EtEQeBIy

Expected/desired behavior

ColumnMenu groups shall work together with multi-column headers

Environment
Kendo UI version: [all]
Browser: [all]