Detect invalid Reference bindings

[mrlacey]

Consider the following in a Xamarin.Forms project:

    <shrp:MaterialFrame
         x:Name="Blurer"
         Padding="0"
         AndroidBlurRadius="10"
         AndroidBlurRootElement="{Binding Source={x:Reference GridContainer}}"
         CornerRadius="0"
         IsClippedToBounds="False"
         MaterialBlurStyle="Dark"
         MaterialTheme="AcrylicBlur"
         StyleId="5555" />

If GridContainer does not exist, the code will build and run fine but will result in a vague, unhelpful, runtime error when navigating to the page with this content:

System.Reflection.TargetInvocationException
Message=Exception has been thrown by the target of an invocation.

There is no more information provided. It's just down to the developer to work out what went wrong.
Adding detection for this can save lots of wasted time.

Note. This may not apply to just XF projects.