Fixes issue with UmbracoHelper in back office when there is not Document.

Adds another overload to BeginUmbracoForm.

src/Umbraco.Web/HtmlHelperRenderExtensions.cs

@@ -306,6 +306,19 @@ namespace Umbraco.Web
 			return html.BeginUmbracoForm(action, typeof(T), additionalRouteVals, htmlAttributes);
 		}
 
+		/// <summary>
+		/// Helper method to create a new form to execute in the Umbraco request pipeline to a surface controller plugin
+		/// </summary>
+		/// <param name="html"></param>
+		/// <param name="action"></param>
+		/// <param name="controllerName"></param>
+		/// <param name="area"></param>
+		/// <returns></returns>
+		public static MvcForm BeginUmbracoForm(this HtmlHelper html, string action, string controllerName, string area)
+		{
+			return html.BeginUmbracoForm(action, controllerName, area, null, new Dictionary<string, object>());
+		}
+
 		/// <summary>
 		/// Helper method to create a new form to execute in the Umbraco request pipeline to a surface controller plugin
 		/// </summary>