Fix a asp.net bug

Fix a asp.net bug:
angular.js:10046 TypeError: Cannot read properties of undefined (reading 'replace')
at $scope.sorticon (user.js:27:18)
at Object.get (angular.js:10821:21)
at Scope.$digest (angular.js:12489:40)
at Scope.$apply (angular.js:12762:24)
at done (angular.js:8357:45)
at completeRequest (angular.js:8571:7)
at xhr.onreadystatechange (angular.js:8510:11)