Created Unassigned: PropertyGrid with System.Windows.Media.Color[] throws NullReferenceException [22419]

I have an object that I'm trying to use with a PropertyGrid and it throws a NullReferenceException when trying to access the Color[] property.

The stack trace looks like:

```
System.NullReferenceException: Object reference not set to an instance of an object.
at Xceed.Wpf.Toolkit.CollectionControlDialog.Clone(Object source) in C:\Users\brian\Documents\Visual Studio 2015\Projects\FevDnDTester\ExtendedWPFToolkitSolution\Src\Xceed.Wpf.Toolkit\CollectionControl\Implementation\CollectionControlDialog.xaml.cs:line 168
at Xceed.Wpf.Toolkit.CollectionControlDialog.OnSourceInitialized(EventArgs e) in C:\Users\brian\Documents\Visual Studio 2015\Projects\FevDnDTester\ExtendedWPFToolkitSolution\Src\Xceed.Wpf.Toolkit\CollectionControl\Implementation\CollectionControlDialog.xaml.cs:line 137
at System.Windows.Window.CreateSourceWindow(Boolean duringShow)
at System.Windows.Window.CreateSourceWindowDuringShow()
at System.Windows.Window.SafeCreateWindowDuringShow()
at System.Windows.Window.ShowHelper(Object booleanBox)
at System.Windows.Window.Show()
at System.Windows.Window.ShowDialog()
at Xceed.Wpf.Toolkit.CollectionControlButton.CollectionControlButton_Click(Object sender, RoutedEventArgs e) in C:\Users\brian\Documents\Visual Studio 2015\Projects\FevDnDTester\ExtendedWPFToolkitSolution\Src\Xceed.Wpf.Toolkit\CollectionControl\Implementation\CollectionControlButton.cs:line 124
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
at System.Windows.Controls.Primitives.ButtonBase.OnClick()
at System.Windows.Controls.Button.OnClick()
at System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
at System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
at System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
at System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
at System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
at System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
at System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
at System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
at System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
at System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
at System.Windows.Input.InputManager.ProcessStagingArea()
at System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
at System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
at System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
at System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
at MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)
```

The Clone function line that is failing is this:

```
var sourceType = source.GetType();
//Get default constructor
var result = sourceType.GetConstructor( new Type[] { } ).Invoke( null );
```

This is because the Color struct does not have any public constructors so the GetConstructor call returns null and Invoke is called on null.

A quick fix might be to check if sourceType.IsClass and if not, just set result to source, something like:

```
if(sourceType.IsClass)
{
result = source;
return result;
}
```

While this won't solve all cases, it will solve the case for value types.