uncaught typeerror无法读取null

Question

发生异常的javascript错误有人可以帮我解决这个问题吗？ 这是我的全部功能

$scope.getAllSubMilestones = function() {
        if (typeof $scope.subMilestones == 'undefined' || $scope.subMilestones.length < 0 || $scope.subMilestones == '') {
            // the array is defined and has at least one element
            var URL = $window.sessionStorage.getItem('HOST_URL') + '/subMilestoneFormObjs';

            function onSuccess(response) {
                $scope.subMilestones = response.data;
                pu_ws_counter++;
                setTimeout(function() {

                    for (var i = 0; i < $scope.subMilestones.length; i++) {
                        var sub_milestone = $scope.subMilestones[i];
                        var selected_sub_milestone = $scope.project.projectSubMilestones;
                        if(selected_sub_milestone != null){
                        for (var j = 0; j < selected_sub_milestone.length; j++) {
                            var s = selected_sub_milestone[j];
                            if (sub_milestone.id == s.subMilestone.id) {
                                //document.getElementById('#' + sub_milestone.id).checked = true;
                                //                                                $('#' + sub_milestone.id).prop('checked', true);
                                $('#' + sub_milestone.id).click();
                            }
                        }
                        }
                    }

我在这条线上收到错误 for (var j = 0; j < selected_sub_milestone.length; j++) {

错误说

  

未捕获的TypeError：无法读取null的属性'length'