Fix for IndexOutOfRangeException when url param is missing closing brace

If you have a controller with a route like "/something/{id" you will get a IndexOutOfRangeException which is not very helpful in determining the cause of the issue. 

With this fix if you forget the closing brace you will get a ArgumentException with the following message "There is an incomplete parameter in this path segment: '{id'. Check that each '{' character has a matching '}' character." which is thrown by the  System.Web.Http.Routing.HttpRouteParser