Hello mathieu cupryk,
Thank you for using our services.
Can you please give us a little bit more information on the method/event in which you are getting the error? From what I can see from the stack trace the Telerik.Cms.Web.UrlHelper.GetProjectName()
method that you are calling returns a null value. Can you try to take out the initialization of the Literal Control outside, perform a check if it is null, and only then add it to the projectName
Please, check the suggested above and get back to us. We will be more than happy to assist you.
the Telerik team