NullReferenceException when using `TrackingCollection.CreateListenerCollection`

[grokys]

The default value for the stickieItemsOnTop in TrackingCollection.CreateListenerCollection is null, but if one tries to use a null here this throws an exception:

var col = new ObservableCollection<T>(stickieItemsOnTop);

As you cannot create an ObservableCollection with a null initializer collection.