Safe access schema property

lib/schemaUtils.js

@@ -2036,10 +2036,11 @@ module.exports = {
       }
 
       setTimeout(() => {
-        if (!schemaPathVar.schema) {
+        if (!(schemaPathVar && schemaPathVar.schema)) {
           // no errors to show if there's no schema present in the spec
           return cb(null, []);
         }
+
         this.checkValueAgainstSchema(mismatchProperty,
           transactionPathPrefix,
           pathVar.key,