RiveControl crashes (null scene) when a RiveInput is bound TwoWay or OneWayToSource and the Source didn't load

A RiveControl whose Source doesn't load (the file is missing, or isn't a Rive file) is harmless: Noesis reports Resource not found (or the Rive runtime prints Bad header), the control stays empty, and the rest of the page works.
But if the control has a RiveInput where InputValue is bound TwoWay or OneWayToSource, the first IView::Update crashes the process with a null read.

   <Grid xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:noesis="clr-namespace:NoesisGUIExtensions;assembly=Noesis.GUI.Extensions">
     <noesis:RiveControl x:Name="Rive" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Source="missing.riv">
       <noesis:RiveInput InputName="Level" InputValue="{Binding Level, Mode=TwoWay}"/>
     </noesis:RiveControl>
   </Grid>