Exception when adding row items to an unbound DataGrid

[kdemuth]

When a DataGrid ItemSource property is not set, adding rows (items) directly to to the DataGrid throws an exception. This works as expected when AdonisUI is disabled, or if row items are added indirectly via a bound ObservableCollection.

I created a small .NET 5.0 WPF application to reproduce the issue:

https://github.com/kdemuth/adonis-ui-test

Test app is a .Net 5.0 WPF C# application created with VS 2019, using AdonisUI 1.17.1