[Checkbox] getValue still NOK

[Jerom138]

The first time "this.state.isChecked" is undefined and getValue must return false

getValue: function getValue() {
        if (this.props.value === undefined || isBoolean(this.props.value)) {
            return this.state.isChecked;
        }
        return this.state.isChecked ? this.props.value : undefined;
    },