What is the required value for the Window argument in RenderView

I am busy migrating a project to null-safety and am running into an issue with the following code snippet:

RenderView(
 child: RenderPositionedBox(
 alignment: Alignment.center,
 child: repaintBoundary,
 ),
 configuration: ViewConfiguration(
 size: logicalSize,
 devicePixelRatio: 1.0,
 ),
 window: null,
)

The window argument is not nullable and requires a FlutterView which is an abstract class, google is not helping me figure out what actually needs to be used there.

Tx