ToCheckbox indeterminateChild raise error and do nothing

[Nyan11]

Hello,

To reproduce

Do it in a Playground:

 ToCheckbox new
                  labelText: 'hello';
                  indeterminateChild;
                  yourself.

My error

[plantec]

The indeterminateChild is initialized when the skin is installed. So if one open the checkbox in a space, then, after the skin has been installed, a #indeterminateChild send answers the BlElement that is used to style an indeterminate state. To try it, open the checkbox in a space and inspect it. Then send #indeterminateChild in the inspector