System.NullReferenceException: Object reference not set to an instance of an object.
   at Umbraco.Web.PublishedContentExtensions.GetPropertyValue(IPublishedContent content, String alias)
   at ASP._Page_Views_Partials_Grid_Editors_DocTypeGridEditor_L4_afbeeldingMetLink_cshtml.Execute() in D:\www\hypotheco.nl\www\Views\Partials\Grid\Editors\DocTypeGridEditor\L4\afbeeldingMetLink.cshtml:line 9
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
   at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
   at Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer)
   at System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection)
   at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
   at Our.Umbraco.DocTypeGridEditor.Web.Extensions.HtmlHelperExtensions.RenderDocTypeGridEditorItem(HtmlHelper helper, IPublishedContent content, String editorAlias, String viewPath, String previewViewPath, Boolean isPreview)
   at ASP._Page_app_plugins_doctypegrideditor_render_doctypegrideditor_cshtml.Execute() in D:\www\hypotheco.nl\www\app_plugins\doctypegrideditor\render\doctypegrideditor.cshtml:line 28
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy()
   at System.Web.Mvc.WebViewPage.ExecutePageHierarchy()
   at System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage)
   at System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance)
   at System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer)
   at Umbraco.Core.Profiling.ProfilingView.Render(ViewContext viewContext, TextWriter writer)
   at System.Web.Mvc.HtmlHelper.RenderPartialInternal(String partialViewName, ViewDataDictionary viewData, Object model, TextWriter writer, ViewEngineCollection viewEngineCollection)
   at System.Web.Mvc.Html.PartialExtensions.Partial(HtmlHelper htmlHelper, String partialViewName, Object model, ViewDataDictionary viewData)
   at ASP._Page_Views_Partials_grid_editors_base_cshtml.Execute() in D:\www\hypotheco.nl\www\Views\Partials\grid\editors\base.cshtml:line 19