DontDestroyOnLoad

Hi
I have some error Unity after use 5.1 change to 5.6.3f
All my image , etc are missing:

InvalidOperationException: The following game object is invoking the DontDestroyOnLoad method: AudioManager. Notice that DontDestroyOnLoad can only be used in play mode and, as such, cannot be part of an editor script.
BaseManager.OnEnable () (at Assets/Bubble Shooter Pet Match 3 Completed/Scripts/Managers/BaseManager.cs:37)


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using UnityEngine;
using System.Collections;

// Is the parent Base manager all other Managers will use AudioClips or other data from
public class BaseManager : ScriptableObject
{

// instance of class (Singleton)
public static BaseManager instance = null;

// audio clips to play looped and fade in/out
public AudioClip menuMusic;
public static GameObject globalMenuMusic;
public AudioClip gameMusic;
public static GameObject globalGameMusic;

// our fade animation clip
public AnimationClip fadeClip;

// audio clips to play one time
public AudioClip sfxButton;
public AudioClip sfxBomb;
public AudioClip sfxSwap;
public AudioClip sfxTouched;
public AudioClip sfxDrop;
public AudioClip sfxReadyGo;
public AudioClip sfxThrow;
public AudioClip sfxVictory;
public AudioClip sfxFailed;

// declare instance
void OnEnable()
{
if (instance == null)
{
instance = this;
DontDestroyOnLoad(this);
}
}

public static BaseManager GetInstance()
{
return instance;
}
}