Error in btn2state extention

Version 3.6
Source: dhtmlxform_item_btn2state.js
Lines: 35-37

item._doOnKeyUpDown = function(evName, evObj, inp) { this.callEvent(evName, [this.childNodes[this._ll?0:1].childNodes[0], e, this._idd]); }
For the callEvent call, the second parameter should likely be evObj instead of an e.

The way it is in the released code, when tabbing over a 2-state button there is an error logged in the console.

How can we reproduce the issue?