Update id-validator.js

Author: esalu

lib/id-validator.js

@@ -63,7 +63,7 @@ IdValidator.prototype.validateSchema = function (
                 validator: function (value, respond) {
                     var conditionsCopy = conditions
                     //A query may not implement an isModified function.
-                    if (!!this.isModified && !this.isModified(path)) {
+                    if (this && !!this.isModified && !this.isModified(path)) {
                         return respond ? respond(true) : true
                     }
                     if (!(self instanceof IdValidator) || self.enabled) {
@@ -105,7 +105,7 @@ function executeQuery (query, conditions, validateValue, respond) {
 function validateId (
     doc, connection, refModelName, value, conditions, respond) {
     if (value == null) {
-        return respond(true)
+        return respond ? respond(true) : true
     }
     var refModel = connection.model(refModelName)
     var query = refModel.countDocuments({_id: value})
@@ -116,7 +116,7 @@ function validateIdArray (
     doc, connection, refModelName, values, conditions, respond,
     allowDuplicates) {
     if (values == null || values.length == 0) {
-        return respond(true)
+        return respond ? respond(true) : true
     }
 
     var checkValues = values