Is there any possible fix for this :https://bugzilla.xamarin.com/show_bug.cgi?id=24681
Have you read these?
http://developer.xamarin.com/guides/cross-platform/macios/updating-xamarin-forms-apps/ (Second part about upgrade to 1.3)
I just had a quick peek on the code for your bug but it could not see that you have upgraded your application class or startup code for 1.3. I suggest you do that first.
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