AdMob奖励视频结束时，Unity应用程序崩溃

Question

在iPhone上使用测试广告，我可以显示奖励广告，但是当它关​​闭时，应用崩溃。我正在使用的功能是：

public void HandleRewardBasedVideoRewarded(object sender, Reward args) {
    MonoBehaviour.print( "HandleRewardBasedVideoRewarded event received");
    StartCoroutine ( gm.noAdsReviveCountdown() );
}

否则，协程运行得很好，所以我认为这与它无关。每次尝试从视频返回到应用程序时，它是否会崩溃？我以为是因为我没有使用sender或args参数？

编辑：添加noAdsReviveCountdown函数：

// No Ad Revive Countdown function - after 3 seconds the game will resume
public IEnumerator noAdsReviveCountdown() {

    continueButton.interactable = false;
    continueText.gameObject.SetActive (false);
    adReviveButton.gameObject.SetActive (false);
    noAdsReviveCountdownText.gameObject.SetActive (true);

    timeLeft = 3;
    while (timeLeft >= 0) {
        noAdsReviveCountdownText.text = timeLeft.ToString();
        noAdsReviveCountdownAnim.ResetTrigger ("CountdownTrigger");
        noAdsReviveCountdownAnim.SetTrigger ("CountdownTrigger");
        yield return new WaitForSecondsRealtime(1.0f);
        timeLeft--;
    }
    if (timeLeft < 0) {
        var balls = GameObject.FindGameObjectsWithTag ("ball");
        foreach (var ball in balls) {
            Destroy (ball);
        }
        noAdsReviveCountdownText.gameObject.SetActive (false);
        continueButton.gameObject.SetActive (false);
        Time.timeScale = 1;
    }

}