Update Pull Request 1170 to not use C# 6 Stuff

ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Controls/LayoutAnchorablePaneControl.cs

@@ -62,10 +62,10 @@ namespace Xceed.Wpf.AvalonDock.Controls
 
         protected override void OnGotKeyboardFocus(System.Windows.Input.KeyboardFocusChangedEventArgs e)
         {
-            if (_model?.SelectedContent != null)
-            {
-                _model.SelectedContent.IsActive = true;
-            }
+             if ((_model != null) && (_model.SelectedContent != null))
+             {
+                 _model.SelectedContent.IsActive = true;
+             }
 
             base.OnGotKeyboardFocus(e);
         }

ExtendedWPFToolkitSolution/Src/Xceed.Wpf.AvalonDock/Controls/LayoutItem.cs

@@ -204,9 +204,15 @@ namespace Xceed.Wpf.AvalonDock.Controls
                     _view = new ContentPresenter();
 
                     _view.SetBinding(ContentPresenter.ContentProperty, new Binding("Content") { Source = LayoutElement });
-                    _view.SetBinding(ContentPresenter.ContentTemplateProperty, new Binding("LayoutItemTemplate") { Source =  LayoutElement?.Root?.Manager});
-                    _view.SetBinding(ContentPresenter.ContentTemplateSelectorProperty, new Binding("LayoutItemTemplateSelector") { Source = LayoutElement?.Root?.Manager });
-                    LayoutElement?.Root?.Manager.InternalAddLogicalChild(_view);
+                    if ((LayoutElement != null) && (LayoutElement.Root != null))
+                     {
+                         _view.SetBinding(ContentPresenter.ContentTemplateProperty, new Binding("LayoutItemTemplate") { Source = LayoutElement.Root.Manager });
+                         _view.SetBinding(ContentPresenter.ContentTemplateSelectorProperty, new Binding("LayoutItemTemplateSelector") { Source = LayoutElement.Root.Manager });
+                         if (LayoutElement.Root.Manager != null)
+                         {
+                             LayoutElement.Root.Manager.InternalAddLogicalChild(_view);
+                         }
+                     }
                 }
 
                 return _view;