### Bug report

Treelist column's filterable property is applied to the wrong field when column locking and a multi-column header is applied.

Reported in: 1446991

### Reproduction of the problem

https://dojo.telerik.com/@Mearaj_6303/EDuhUlOG

### Current behavior

The Filter from "Position" is hidden.

### Expected/desired behavior

The Filter from "Phone" is hidden.

### Environment

* **Kendo UI version:** 2019.3.1023
* **Browser:** [all]