fix weird NRE theme binder

Assets/ThemeVfxBinder.cs

@@ -26,4 +26,14 @@ public class ThemeVfxBinder : VFXBinderBase {
     public override void UpdateBinding(VisualEffect component) {
         component.SetGradient(ThemeParameter, themeSelector.CurrentTheme());
     }
+
+
+    // have to override these to prevent NRE
+    protected override void OnEnable() {
+        // Debug.Log("OnEnable");
+    }
+
+    protected override void OnDisable() {
+        // Debug.Log("OnDisable");
+    }
 }