b#31688 InsertBefore Android Crash

stack trace

12-16 10:10:57.751 I/MonoDroid( 4383): UNHANDLED EXCEPTION:
12-16 10:10:57.751 I/MonoDroid( 4383): System.ArgumentException: before must be a child of the NavigationPage
12-16 10:10:57.751 I/MonoDroid( 4383): Parameter name: before
12-16 10:10:57.751 I/MonoDroid( 4383):   at Xamarin.Forms.NavigationPage.InsertPageBefore (Xamarin.Forms.Page page, Xamarin.Forms.Page before) [0x00013] in C:\BuildAgent2\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationPage.cs:301 
12-16 10:10:57.751 I/MonoDroid( 4383):   at Xamarin.Forms.NavigationPage+NavigationImpl.OnInsertPageBefore (Xamarin.Forms.Page page, Xamarin.Forms.Page before) [0x00000] in C:\BuildAgent2\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationPage.cs:423 
12-16 10:10:57.751 I/MonoDroid( 4383):   at Xamarin.Forms.NavigationProxy.InsertPageBefore (Xamarin.Forms.Page page, Xamarin.Forms.Page before) [0x00000] in C:\BuildAgent2\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:57 
12-16 10:10:57.751 I/MonoDroid( 4383):   at Xamarin.Forms.NavigationProxy.OnInsertPageBefore (Xamarin.Forms.Page page, Xamarin.Forms.Page before) [0x0003e] in C:\BuildAgent2\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:153 
12-16 10:10:57.751 I/MonoDroid( 4383):   at Xamarin.Forms.NavigationProxy.InsertPageBefore (Xamarin.Forms.Page page, Xamarin.Forms.Page before) [0x00000] in C:\BuildAgent2\work\ca3766cfc22354a1\Xamarin.Forms.Core\NavigationProxy.cs:57 
12-16 10:10:57.751 I/MonoDroid( 4383):   at XamFormsNavigation.Droid.MyApp+MyMainPage+<LoadAsync>d__3.MoveNext () [0x0001d] in D:\Xamarin Work\_Bugs\31688 insertbefore crash\XamFormsNavigation\XamFormsNavigation\XamFormsNavigation.Droid\MyApp.cs:34 
12-16 10:10:57.751 I/MonoDroid( 4383): --- End of stack trace from previous location where exception was thrown ---
12-16 10:10:57.751 I/MonoDroid( 4383):   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/3511/77cb8568/source/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143 
12-16 10:10:57.751 I/MonoDroid( 4383):   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>m__0 (System.Object state) [0x00000] in /Users/builder/data/lanes/3511/77cb8568/source/mono/mcs/class/referencesource/mscorlib/system/runtime/compilerservices/AsyncMethodBuilder.cs:1018 
12-16 10:10:57.751 I/MonoDroid( 4383):   at Android.App.SyncContext+<Post>c__AnonStorey0.<>m__0 () [0x00000] in /Users/builder/data/lanes/3511/ce955cc0/source/xamarin-android/src/Mono.Android/Android.App/SyncContext.cs:18 
12-16 10:10:57.751 I/MonoDroid( 4383):   at Java.Lang.Thread+RunnableImplementor.Run () [0x0000b] in /Users/builder/data/lanes/3511/ce955cc0/source/xamarin-android/src/Mono.Android/Java.Lang/Thread.cs:36 
12-16 10:10:57.751 I/MonoDroid( 4383):   at Java.Lang.IRunnableInvoker.n_Run (System.IntPtr jnienv, System.IntPtr native__this) [0x00009] in /Users/builder/data/lanes/3511/ce955cc0/source/monodroid/src/Mono.Android/platforms/android-24/src/generated/Java.Lang.IRunnable.cs:81 
12-16 10:10:57.751 I/MonoDroid( 4383):   at (wrapper dynamic-method) System.Object:19e01d31-c387-4234-b7b1-fc1acce208ca (intptr,intptr)
12-16 10:10:57.755 D/Mono    ( 4383): DllImport searching in: '__Internal' ('(null)').
12-16 10:10:57.755 D/Mono    ( 4383): Searching for 'java_interop_jnienv_throw'.
12-16 10:10:57.755 D/Mono    ( 4383): Probing 'java_interop_jnienv_throw'.
12-16 10:10:57.755 D/Mono    ( 4383): Found as 'java_interop_jnienv_throw'.
An unhandled exception occured.

12-16 10:10:58.515 E/mono    ( 4383): 
12-16 10:10:58.515 E/mono    ( 4383): Unhandled Exception:
12-16 10:10:58.515 E/mono    ( 4383): System.ArgumentException: before must be a child of the NavigationPage
12-16 10:10:58.515 E/mono    ( 4383): Parameter name: before
In mgmain JNI_OnLoad
12-16 10:10:58.515 E/mono-rt ( 4383): [ERROR] FATAL UNHANDLED EXCEPTION: System.ArgumentException: before must be a child of the NavigationPage
12-16 10:10:58.515 E/mono-rt ( 4383): Parameter name: before