Tidy Stack

System.NullReferenceException: Object reference not set to an instance of an object.
at GetUserById() in C:ProjectsMyAppServicesUserService.cs:line 45
at GetDetails() in C:ProjectsMyAppControllersUserController.cs:line 30
at InvokeActionMethodAsync()
at InvokeNextActionFilterAsync()
at InvokeNextResourceFilter()
at Invoke()
at Invoke()
at ProcessRequestsAsync()