Null Reference Exception on Android & iOS in LoadAdError.GetMessage()

[REQUIRED] Step 1: Describe your environment

• Unity version: 2021.3.1f1
• Google Mobile Ads Unity plugin version: GoogleMobileAds-v7.3.0
• Platform: iOS, Android
• Platform OS version: Android 12, iOS 15.7.1
• Any specific devices issue occurs on: iPhone SE, Poco X3 Pro
• Mediation ad networks used, and their versions: None

[REQUIRED] Step 2: Describe the problem

Steps to reproduce:

Import GoogleMobileAds-v7.3.0 into your project. Subscribe to BannerView.OnAdFailedToLoad and in the subscribed method Debug.Log the result of this method LoadAdError.GetMessage() that is called on OnAdFailedToLoad event argument. Ensure Thread safety. Compile it onto Android & iOS Make conditions so an ad doesn’t load. (turn off your internet connection) Observe the result:

Android: Null Reference Exception in IAdErrorClient inherited class. iOS: Thread 1: EXC_BAD_ACCESS (code=2, address=0x16fc77e80) Application Crash.

Relevant Code:

    _bannerView = new BannerView(AdmobConstants.BannerAdUnitId, AdSize.Banner, AdPosition.Top);
    _bannerView.OnAdFailedToLoad += FailedToLoadHandler;

            private void FailedToLoadHandler(object sender, AdFailedToLoadEventArgs e)
            {
                YourUnityClass.ExecuteFromMainThread(() =>
                {
                    Debug.Log($"{e?.LoadAdError.GetMessage()}");
                });
            }

[NVentimiglia]

Hi @mkprivates thanks for raising awareness, I will look deeper into this issue. That said, here is a work around.

private void FailedToLoadHandler(object sender, AdFailedToLoadEventArgs e)
            {
                string errorMessage = e?.LoadAdError.GetMessage();
                MobileEventsExecutor.ExecuteFromMainThread(() =>
                {
                    Debug.Log(errorMessage);
                });
            }

Explanation is this could be a race condition related to releasing of resources in IOS.

[NVentimiglia]

@Hetagkaty

This error is cause by accessing a native object after it is disposed. This can be solved by making sure the object is accessed in the same frame as it is messaged.

private void FailedToLoadHandler(object sender, AdFailedToLoadEventArgs e)
            {
                string errorMessage = e.LoadAdError.GetMessage();
                // Code executed in this function are executed at a later time.
                // The native object may be cleaned up already, resulting in the null.
                MobileEventsExecutor.ExecuteFromMainThread(() =>
                {
                    Debug.Log(errorMessage);
                });
            }