NullReferenceException: Object reference not set to an instance of an object IN BLEND FOR VISUAL STUDIO

Question

GETTING THE FOLLOWING ERROR

An Exception was thrown.

   at Microsoft.Expression.WindowsPhone.UserInterface.DefaultPhoneThemeValuesHelper.GetDefaultValue(IViewResourceDictionary themeResources, IPropertyId propertyId, String fallbackResourceName, DocumentCompositeNode rootNode, Type resultType, Object& value)
   at Microsoft.Expression.WindowsPhone.UserInterface.DefaultPhoneThemeValuesHelper.UpdateDefaultThemeProperties(IProjectContext projectContext, Control control, IEnumerable`1 properties)
   at Microsoft.Expression.WindowsPhone.UserInterface.DefaultPhoneThemeValuesHelper.View_ViewContentChanged(Object sender, EventArgs e)
   at Microsoft.Expression.DesignSurface.View.SilverlightSceneView.SetViewContentWorker(ViewContentType contentType, ViewNode target, Object content)
   at Microsoft.Expression.DesignSurface.View.SilverlightSceneView.SetViewContentInternal(ViewContentType contentType, ViewNode target, Object content)
   at Microsoft.Expression.DesignSurface.View.XamlSceneView.Microsoft.Expression.Platform.InstanceBuilders.IAttachViewRoot.EnsureRootSited()
   at Microsoft.Expression.Platform.InstanceBuilders.ViewNodeManager.EnsureRootSited(IAttachViewRoot siteRoot)