[WinUI] nre at CommunityToolkit.WinUI.Media.Pipelines.PipelineBuilder

### Describe the bug

Getting null reference exception on a **WinUI** application when using ```UIElementExtensions.VisualFactory```

### Regression

_No response_

### Reproducible in sample app?

- [ ] This bug can be reproduced in the sample app.

### Steps to reproduce

```text
Stack trace:
_at CommunityToolkit.WinUI.Media.Pipelines.PipelineBuilder.d__9.MoveNext()
at CommunityToolkit.WinUI.Media.PipelineVisualFactoryBase.d__0.MoveNext()
at System.Threading.Tasks.ValueTask`1.get_Result()
at CommunityToolkit.WinUI.Media.PipelineVisualFactory.d__8.MoveNext()
at System.Threading.Tasks.ValueTask`1.get_Result()
at CommunityToolkit.WinUI.Media.UIElementExtensions.d__3.MoveNext()
at System.Threading.Tasks.Task.<>c.b__128_0(Object state)
at Microsoft.UI.Dispatching.DispatcherQueueSynchronizationContext.<>c__DisplayClass2_0.b__0()_

use the following xaml:

the project references:

CommunityToolkit.Mvvm 8.2.1
CommunityToolkit.WinUI.Behaviors 8.0.230907
CommunityToolkit.WinUI.Media 8.0.230907
CommunityToolkit.WinUI.UI.Controls 7.1.2
Microsoft.Extensions.Hosting 6.0.1
Microsoft.WindowsAppSDK 1.3.230502000
Microsoft.Xaml.Behaviors.WinUI.Managed 2.0.9
System.Configuration.ConfigurationManager 7.0.0
WinUIEx 2.2
```

### Expected behavior

no nre

### Screenshots

_No response_

### Windows Build Number

- [ ] Windows 10 1809 (Build 17763)
- [ ] Windows 10 1903 (Build 18362)
- [ ] Windows 10 1909 (Build 18363)
- [ ] Windows 10 2004 (Build 19041)
- [ ] Windows 10 20H2 (Build 19042)
- [ ] Windows 10 21H1 (Build 19043)
- [ ] Windows 11 21H2 (Build 22000)
- [ ] Other (specify)

### Other Windows Build number

_No response_

### App minimum and target SDK version

- [ ] Windows 10, version 1809 (Build 17763)
- [ ] Windows 10, version 1903 (Build 18362)
- [ ] Windows 10, version 1909 (Build 18363)
- [ ] Windows 10, version 2004 (Build 19041)
- [ ] Other (specify)

### Other SDK version

_No response_

### Visual Studio Version

_No response_

### Visual Studio Build Number

_No response_

### Device form factor

_No response_

### Nuget packages

_No response_

### Additional context

_No response_

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