Bug: Removing TabItems from a TabCollection throws NullReferenceException

[minimalism]

To reproduce:

TabControl tabControl = new();
tabControl.Items.Add(new TabItem("Tab Item"));
tabControl.Items.Clear();
// tabControl.Items.RemoveAt(0); exhibits the same behavior

The setter on ListButton.IsPressed will throw when accessing Parent on line 20, which will be null at this point.
I believe the TabItem's Selector will have a Grid InternalChild, whose WidgetsOnCollectionChanged method will unset the Parent property.

[rds1983]

Should be fixed.