Incorrectly configured route causes a NRE from LinksTransformationBuilder.AddRoutePath

[jamiecoh]

An incorrectly configured route, for example badly defined parameters

// Note: id in attr vs myObjectId as param name
[HttpGet("{id:int}",Name="MyBadRoute")
public async Task<MyObject> GetMyObject(int myObjectId)
{
}

And routed via RequiresRoutedLink

options.AddPolicy<MyObject>(policy => policy.RequiresRoutedLink("blah","MyBadRoute",x => new {myObjectId = x.MyObjectId});

Will cause a NullReferenceException due to GetVirtualPath returning null in LinksTransformationBuilderExtensions

...
var virtualPathData = ctx.Router.GetVirtualPath(virtualPathContext);
return virtualPathData.VirtualPath;

[jamiecoh]

Intention is to improve error handling around transformation and raising a more meaningful error. I dont think anyone would want this situation to succeed (ie, give a partial link back) so errors during transformation will raise a LinkTransformationException.