[Bug][Checkbox] Wrong aria-checked

[iadnonov]

I'm submitting a...

• Bug report

Current behavior

CheckBox generate axe error with value={null} and aria-checked="mixed"

Expected behavior

CheckBox should not generate axe error with value={null}

Minimal reproduction of the problem with instructions

1. Open the following link: https://www.telerik.com/kendo-react-ui/components/inputs/checkbox/
2. Make axe DevTools test of the demo.

Ticket ID: 1640852