I'm getting an error when trying to activate a webpart. It activates fine in one setup , but fails in a different one. Administrator in both. Seems like it fails because it's not able to create the list. The error is: Message: Value cannot be null. Stack Trace: at Microsoft.Sharepoint.SPRoleAssignment..ctor at ClientRequestHandler.CreateList(...

private static void CreateLists()
    {            
        try
        {
            SPSecurity.RunWithElevatedPrivileges(delegate()
            {
                using (SPSite site = SPContext.Current.Site)
                {
                    using (SPWeb web = site.RootWeb)
                    {
                        string listName = LIST_NAME;
                        bool listExist = ContainList(web, listName);

                        if (!listExist)
                        {
                            AddFieldDelegate _delegate = new AddFieldDelegate(AddAttachmentFields);
                            SPList list = CreateList(web, listName, _delegate);
                            RegisterList(web, list, KEY);

                        }                            
                    }
                }
            });
        }
        catch (Exception ex)
        {
            throw new Exception(String.Format("Message: {0} Stack Trace: {1}", ex.Message, ex.StackTrace.ToString())); 
        }

    }   private static SPList CreateList(SPWeb web, string listName, AddFieldDelegate _delegate)
    {
        web.AllowUnsafeUpdates = true;

        SPListTemplateType genericList = new SPListTemplateType();
        genericList = SPListTemplateType.GenericList;

        Guid listGuid = web.Lists.Add(listName, "List", genericList);

        SPList list = web.Lists[listGuid];
        list.Hidden = true;

        SPView view = _delegate(list); 

        view.Update();

        //Remove permissions from the list
        list.BreakRoleInheritance(false);

        //Make site owners the list administrators 
        SPPrincipal principal = web.AssociatedOwnerGroup as SPPrincipal;
        SPRoleAssignment assignment = new SPRoleAssignment(principal);
        assignment.RoleDefinitionBindings.Add(web.RoleDefinitions.GetByType(SPRoleType.Administrator));
        list.RoleAssignments.Add(assignment);

        //update list changes
        list.Update();
        return list;
    }