### Bug report

When the columns of the Kendo UI TreeList have the attributes option set, a JavaScrip error is thrown. 

### Reproduction of the problem

1. Set the attributes property for any of the columns in the TreeList.

2. Call the setOptions() method.

3. An error in the console is present.

https://dojo.telerik.com/OKUnEDiJ

### Environment

* **Kendo UI version:** 2020.3.1118
* **jQuery version:** 1.12.4
* **Browser:** [all[]