Copy action on "Difference" hunk item when it is a changed file from "Commits" tab

[Evgeny Kralko]

Value cannot be null.
Parameter name: text

System.ArgumentNullException: Value cannot be null.
Parameter name: text
at System.Windows.Clipboard.SetText(String text)
at Cong.ListBoxController`2.CopySelectedItems() in C:\Repositories\Cong\Cong\Extensions\ListBoxController.cs:line 615
at Cong.ListBoxController`2.<InitializeItem>b__20_0(Object sende, RoutedEventArgs e) in C:\Repositories\Cong\Cong\Extensions\ListBoxController.cs:line 120
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.MenuItem.InvokeClickAfterRender(Object arg)
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)