How to set AdListener to null

Question

I have a banner ad and its callbacks that I display but when I finish the activity LeakCanary shows a memory leak:

com.android.gms,ads.nonagon.ad.webview

Leaking: YES (View.mContext references a destroyed activity)

I destroy the adView in onDestroy but the leak still occurs. I think the problem could be from binding.adView.adListener = object : AdListener() { }. How can I set adListener to null in onDestroy?

override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {

    val adRequest = AdRequest.Builder().build()
    binding.adView.loadAd(adRequest)

    binding.adView.adListener = object : AdListener() {
         // callbacks ...
    }
}

override fun onDestroy() {
    super.onDestroy()

    binding.adView.destroy()
}

XML file:

<com.google.android.gms.ads.AdView
    xmlns:ads="http://schemas.android.com/apk/res-auto"
    android:id="@+id/adView"
    ads:adSize="BANNER"
    ads:adUnitId="ca-app-pub-3940256099942544/6300978111">
    // ...
</com.google.android.gms.ads.AdView>