1) Open a test project with both a web test and an empty manual test
2) Open the empty manual test
3) Drag and drop the web test from the project panel onto the empty step 1 of the manual step

Expected: Nothing to happen
Actual: Test Studio crashes with this stack trace
[02/25 21:12:53,Telerik.TestStudio.exe(13524:1)] First trace message from process 13524: "C:\Program Files (x86)\Telerik\Test Studio\Bin\Telerik.TestStudio.exe" 
[02/25 21:12:53,Telerik.TestStudio.exe(13524:1)] First trace message from foreground thread "Application start thread" (managed ID = 1, native ID = 16668).
[02/25 21:12:53,Telerik.TestStudio.exe(13524:1),Uncategorized] Orchestrator._iUIProject_TestSelected() : Test 'ManualTest(1)' selected.
[02/25 21:13:02,Telerik.TestStudio.exe(13524:1),Error] App.LogUnhandledException() : EXCEPTION! (see below)
     Situation: Unhandled exception!
     Outer Exception Type: System.ArgumentNullException
     Message: Value cannot be null.
          Parameter name: source
     HRESULT: 0x80004003 (Official ID (if app.) = E_POINTER, Error Bit = FAILED, Facility = FACILITY_NULL, Code = 16387)
     Call Stack:
          at System.Linq.Enumerable.Contains[TSource](IEnumerable`1 source, TSource value, IEqualityComparer`1 comparer)
          at System.Linq.Enumerable.Contains[TSource](IEnumerable`1 source, TSource value)
          at ArtOfTest.WebAii.Design.UI.DragDropBehavior.OnDrop(Object sender, DragEventArgs e)
          at Telerik.Windows.DragDrop.DragEventArgs.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.RaiseEvent(RoutedEventArgs e)
          at Telerik.Windows.DragDrop.IInputElementExtensions.RaiseEvent(DependencyObject d, RoutedEventArgs routedEventArgs)
          at Telerik.Windows.DragDrop.DragDropManager.DelegateHelper.OnDragEventHandler(Object sender, DragEventArgs e)
          at Telerik.Windows.DragDrop.DragDropManager.DelegateHelper.OnDrop(Object sender, DragEventArgs e)
          at System.Windows.DragEventArgs.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.RaiseEvent(RoutedEventArgs e)
          at System.Windows.OleDropTarget.RaiseDragEvent(RoutedEvent dragEvent, Int32 dragDropKeyStates, Int32& effects, DependencyObject target, Point targetPoint)
          at System.Windows.OleDropTarget.MS.Win32.UnsafeNativeMethods.IOleDropTarget.OleDrop(Object data, Int32 dragDropKeyStates, Int64 point, Int32& effects)
          at MS.Win32.UnsafeNativeMethods.DoDragDrop(IDataObject dataObject, IOleDropSource dropSource, Int32 allowedEffects, Int32[] finalEffect)
          at System.Windows.OleServicesContext.OleDoDragDrop(IDataObject dataObject, IOleDropSource dropSource, Int32 allowedEffects, Int32[] finalEffect)
          at System.Windows.DragDrop.OleDoDragDrop(DependencyObject dragSource, DataObject dataObject, DragDropEffects allowedEffects)
          at System.Windows.DragDrop.DoDragDrop(DependencyObject dragSource, Object data, DragDropEffects allowedEffects)
          at Telerik.Windows.DragDrop.DragDropManager.DoDragDrop(DependencyObject dragSource, Object data, DragDropEffects allowedEffects, DragDropKeyStates initialKeyState, Object dragVisual, Point relativeStartPoint, Point dragVisualOffset)
          at Telerik.Windows.DragDrop.DragInitializer.StartDrag()
          at Telerik.Windows.DragDrop.DragInitializer.StartDragPrivate(UIElement sender)
          at Telerik.Windows.DragDrop.DragInitializer.DragSourceOnMouseMove(Object sender, MouseEventArgs e)
          at System.Windows.Input.MouseEventArgs.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 MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)