挖空扩展可观察 取消引用时返回未定义

我在Javascript中有一个"对象"，它创建了一个扩展的可观察量，Location等。

当我尝试用值填充项目时，似乎只有 Internet Explorer 11 中会抛出一个错误，指出它是"无法使用未定义或空引用的属性'Address1'"。

奇怪的是，当我进入控制台并输入"self"时，它将位置显示为可观察量。 如果我输入"自我。位置"，它显示了可观察量的功能。 如果键入"自我。位置（）"，它说未定义。 几乎所有其他事情似乎都还可以。 我包含两个可观察量的代码。 一个（位置）导致问题。 另一个是参与者，在代码中看起来很相似，但"观察"得很好。

    self.Participants = ko.observableArray([]).extend({
        validation: [{
            validator: function (value) {
                if ((showConfig && showConfig.CreateWorkOrder) || (showConfig && showConfig.WorkOrderNumber) || (showConfig && showConfig.WorkOrderId)) {
                    self.ModelErrors({ sort: 7, element: "participants-container", error: "", clear: true });
                    return true;
                }
                var HasGroupRoute = self.GroupRoute() != "g0";
                if (HasGroupRoute) {
                    self.ModelErrors({ sort: 7, element: "participants-container", error: "", clear: true });
                    return true;
                }
                if ((!value || value.length <= 0) || HasGroupRoute) {
                    //$("#participants-container").addClass('sp-error');
                    //$("#divErrMsgBlock").show();
                    //addressError.push("<li style='text-align: left; list-style-type: square'>You must select a participant.</li>");
                    self.ModelErrors({ sort: 7, element: "participants-container", error: "<li style='text-align: left; list-style-type: square'>You must select a participant.</li>" });
                    return false;
                }
                else {
                    //$("#participants-container").removeClass('sp-error');
                    //$("#divErrMsgBlock").hide();
                    self.ModelErrors({ sort: 7, element: "participants-container", error: "", clear: true });
                    return true;
                }
            },
            message: '',
        }]
    });
    self.Location = ko.observable().extend({
        validation: [{
            validator: function (value) {
                if (value == undefined) return;                    
                var Address1 = (value.Address1() == undefined ? null : value.Address1());
                var City = (value.City() == undefined ? null : value.City()); 
                var State = (value.StateOrProvince() == undefined ? null : value.StateOrProvince()); 
                var Zip = (value.PostalCode() == undefined ? null : value.PostalCode());
                var _mustCheck = (self.AppointmentType() == "4" || self.JobReference() != undefined) || (Address1 != null && Address1 != '') || (Address1 != null && Address1 != '') || (City != null && City != '') || (Zip != null && Zip != '');
                var _missing = (Address1 == undefined || Address1 == null) || (City == undefined || City == null) || (State == undefined || State == null) || (Zip == undefined || Zip == null);
                if (_mustCheck && _missing) {
                    //addressError.push("<li style='text-align: left; list-style-type: square'>Address is not complete.</li>");
                    self.ModelErrors({ sort: 8, element: "location-container", error: "<li style='text-align: left; list-style-type: square'>Address is not complete.</li>" });
                    if (value.Address1() == null || value.Address1() == '') {
                        //$("#appt-address1").addClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "appt-address1", error: "", clear: false });
                    }
                    else {
                        //$("#appt-address1").removeClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "appt-address1", error: "", clear: true });
                    }
                    if (value.City() == null || value.City() == '') {
                        //$("#appt-city").addClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "appt-city", error: "", clear: false });
                    }
                    else {
                        //$("#appt-city").removeClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "appt-city", error: "", clear: true });
                    }
                    if (value.StateOrProvince() == undefined || value.StateOrProvince() == '') {
                        //$("#cmboStates").addClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "cmboStates", error: "", clear: false });
                    }
                    else {
                        //$("#cmboStates").removeClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "cmboStates", error: "", clear: true });
                    }
                    if (value.PostalCode() == null || value.PostalCode() == null) {
                        //$("#appt-zip").addClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "appt-zip", error: "", clear: false });
                    }
                    else {
                        //$("#appt-zip").removeClass('sp-error');
                        self.ModelErrors({ sort: 8, element: "appt-zip", error: "", clear: true });
                    }
                } else {
                    self.ModelErrors({ sort: 8, element: "location-container", error: "", clear: true });
                    self.ModelErrors({ sort: 8, element: "appt-address1", error: "", clear: true });
                    self.ModelErrors({ sort: 8, element: "appt-city", error: "", clear: true });
                    self.ModelErrors({ sort: 8, element: "cmboStates", error: "", clear: true });
                    self.ModelErrors({ sort: 8, element: "appt-zip", error: "", clear: true });
                }
            },
            message: ''
        }]
    });

在 IE11 中导致错误的行是这样的：

 self.Location().Address1(model.Address1);