Why is clicking too fast giving me a missingReferenceException in Unity?

Question

I made a small method that will quickly give the player a "flashlike" display when a sheep is killed. However clicking too fast will trigger a missingReferenceException. Because it registers the raycast a second time. Is this due to the delay on the DestroyObject() or something else?

private IEnumerator startFlashing(GameObject sheep)
{  
    sheep.gameObject.GetComponent<Rigidbody>().freezeRotation = true;
    sheep.gameObject.GetComponent<Rigidbody>().velocity = Vector3.zero;
    sheep.SetActive(false);
    yield return new WaitForSeconds(theTimeBetweenFlashes);
    sheep.SetActive(true);
    DestroyObject(sheep.gameObject, 0.1f);    
}

Answer 1

With the support of @DMGregory, I will post my comment as an answer :

When calling DestroyObject (which surely calls Destroy), the sheep object and its components (rigidbody) will turn to true a flag saying "I will be destroyed".

When you retrieve the Rigidbody using GetComponent, the function checks this flags and warns you with the message.

I advise you to define a boolean you set to false in the DestroyObject function indicating your sheep can't be clicked anymore :

private bool destroyInProgress = false ;

private IEnumerator startFlashing(GameObject sheep)
{
    if( destroyInProgress ) yield break ;

    sheep.gameObject.GetComponent<Rigidbody>().freezeRotation = true;
    sheep.gameObject.GetComponent<Rigidbody>().velocity = Vector3.zero;
    sheep.SetActive(false);
    yield return new WaitForSeconds(theTimeBetweenFlashes);
    sheep.SetActive(true);
    DestroyObject(sheep.gameObject, 0.1f);
    destroyInProgress = true ;
}