The value is null after the MonoScript field is assigned in inspector

[Breamax]

I wrote the following script.

public class DocumentAsset : ScriptableSingleton<DocumentAsset>
{
    public Texture configTex1;
    public Texture configTex2;
}

I found a strange problem with configTex1 getting the value I set on the panel through instance, but configTex2 is null.