[Solved] Why this code show error?

public class SettingUIController : UdonSharpBehaviour
{
    //...

    [SerializeField] private Slider sli_bloom;

    //...

    private void Start()
    {
        Init();
    }

    public void Init()
    {
        sli_bloom.value = 0.7f; //Error

        //...
    }
}

Hi, I create post setting ui. This code will be fine on Editor, but after Build&Test, this code show this error.

What am i missing? Thanks.
.
.
.
.
.
------------------------------ [Solved] ------------------------------

public class ImageChangeToggle : Toggle
//...

Cause is this script. I override ‘Toggle’ in my custom script. But it’s not working…

public class SettingUIController : UdonSharpBehaviour
{
//...
    [SerializeField] private Toggle tgl_play;
//...
}

When use ‘ImageChangeToggle’ in ‘SettingUIController’ like this code, ‘SerializeField’ is to null.