CollectionViewHandler2 null reference exception if ItemsLayout is set for Tablet but NOT Phone

[rysbilinski]

Description

Adding a collectionview to a page and only setting the ItemsLayout property for Tablet will throw a null reference exception before the page appears on mobile.

Steps to Reproduce

1. Add A collectionview to a page, and add the following to the collection view:

<CollectionView ItemsLayout="{OnIdiom Tablet='VerticalGrid 2'}" ItemsSource="{Binding Items}" VerticalOptions="Fill">

2. Configure builder to use the new CollectionViewHandler2:

builder.ConfigureMauiHandlers(handlers =>
                {

                    handlers.AddHandler<Microsoft.Maui.Controls.CollectionView, Microsoft.Maui.Controls.Handlers.Items2.CollectionViewHandler2>();

                    handlers.AddHandler<Microsoft.Maui.Controls.CarouselView, Microsoft.Maui.Controls.Handlers.Items2.CarouselViewHandler2>();

                });

3. Run the application on iOS
4. Navigate to the page and you will see a crash in Program.cs

System.NullReferenceException: 'Object reference not set to an instance of an object.'

Link to public reproduction project repository

https://github.com/rysbilinski/CollectionViewHandler2Bugs

Version with bug

9.0.10 SR1

Is this a regression from previous behavior?

Yes, this used to work in .NET MAUI

Last version that worked well

8.0.100 SR10

Affected platforms

iOS

Affected platform versions

No response

Did you find any workaround?

Workaround was to add the "phone" OnIdiom parameter:

<CollectionView ItemsLayout="{OnIdiom Phone='VeritcalGrid', Tablet='VerticalGrid 2'}" ItemsSource="{Binding Items}" VerticalOptions="Fill">

Relevant log output