ShadowExtensions.GetAlphaMaskAsync causing "Value does not fall within the expected range" on project start, crashing

### Description

This is a strange new error I am getting frequently on starting up my project in Windows on Debug. It looks like as follows. It crashes the project.

I am skeptical I will be able to reproduce this in a simple project. I am not sure what it represents. We certainly never had this before. I presume one of the shadow optimizations has a but.

### Steps to Reproduce

### Link to public reproduction project repository

n/a

### Version with bug

9.0.90 SR9

### Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

### Last version that worked well

Unknown/Other

### Affected platforms

Windows

### Affected platform versions

_No response_

### Did you find any workaround?

_No response_

### Relevant log output

```shell

```