Q:can not change UIToggle State by code (fixed)

[chaosngui]

var tab0 = GameObject.FindGameObjectWithTag("Tab0").GetComponent<UIToggle>();
            tab0.value = true;
it works and the state of tab0 changed to be checked;

var tab1 = GameObject.FindGameObjectWithTag("Tab1").GetComponent<UIToggle>();
            tab1.value = false;
this doesn't work,and tab1 is still checked.

fixed: allow to choose none