Fix to NavigationPageRenderer constructor crash

FixedNavigationRenderer.cs

using System;
using Android.Runtime;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android.AppCompat;

[assembly: ExportRenderer (typeof (NavigationPage), typeof (MyApp.Droid.Renderers.FixedNavigationRenderer))]
namespace MyApp.Droid.Renderers
{
	// WARNING
	// There is a crash happens for unknown reason:
	// System.MissingMethodException: No constructor found for 
	//   Xamarin.Forms.Platform.Android.AppCompat.NavigationPageRenderer::.ctor(System.IntPtr, Android.Runtime.JniHandleOwnership)
	// see https://bugzilla.xamarin.com/show_bug.cgi?id=40258
	// --
	// As a solution we override NavigationPageRenderer to provide the constructor.
	// Although then there is a NullReferenceException happens in 
	//  OnDetachedFromWindow() method which we are fixing too.
	public class FixedNavigationRenderer: NavigationPageRenderer
	{
		public FixedNavigationRenderer()
			: base ()
		{}

		public FixedNavigationRenderer (IntPtr javaReference, JniHandleOwnership transfer)
			: base ()
		{
		}

		protected override void OnDetachedFromWindow ()
		{
			if (Element == null)
			{
				return;
			}
			base.OnDetachedFromWindow ();
		}
	}
}

@midix have you managed to minimize total occurrences of such crashes?