Make TabControl show from XAML.

Perspex.Controls/ItemsControl.cs

@@ -36,7 +36,7 @@ namespace Perspex.Controls
         /// Defines the <see cref="Items"/> property.
         /// </summary>
         public static readonly PerspexProperty<IEnumerable> ItemsProperty =
-            PerspexProperty.Register<ItemsControl, IEnumerable>("Items", defaultValue: new Collection<object>());
+            PerspexProperty.Register<ItemsControl, IEnumerable>("Items");
 
         /// <summary>
         /// Defines the <see cref="ItemsPanel"/> property.
@@ -60,6 +60,7 @@ namespace Perspex.Controls
         public ItemsControl()
         {
             this.Classes.Add(":empty");
+            this.Items = new PerspexList<object>();
         }
 
         /// <summary>

Perspex.Themes.Default/TabControlStyle.cs

@@ -43,7 +43,7 @@ namespace Perspex.Themes.Default
                     new TabStrip
                     {
                         Name = "tabStrip",
-                        [~TabStrip.ItemsProperty] = control[~TabControl.ItemsProperty],
+                        [!TabStrip.ItemsProperty] = control[!TabControl.ItemsProperty],
                         [!!TabStrip.SelectedItemProperty] = control[!!TabControl.SelectedItemProperty],
                     },
                     new Deck
@@ -53,7 +53,7 @@ namespace Perspex.Themes.Default
                         {
                             new DataTemplate<TabItem>(x => (Control)control.MaterializeDataTemplate(x.Content)),
                         },
-                        [~Deck.ItemsProperty] = control[~TabControl.ItemsProperty],
+                        [!Deck.ItemsProperty] = control[!TabControl.ItemsProperty],
                         [!Deck.SelectedItemProperty] = control[!TabControl.SelectedItemProperty],
                         [~Deck.TransitionProperty] = control[~TabControl.TransitionProperty],
                         [Grid.RowProperty] = 1,