Json schema default value improvement (#964)

* Ensure value has property before using its value

* Add tests

1 files changed, 2 insertions, 1 deletions

diff --git a/ext/bg/js/json-schema.js b/ext/bg/js/json-schema.js
index adb71fa3..ea1531ab 100644
--- a/ext/bg/js/json-schema.js
+++ b/ext/bg/js/json-schema.js
@@ -637,7 +637,8 @@ class JsonSchemaValidator {
                 if (propertySchema === null) { continue; }
                 info.valuePush(property, value);
                 info.schemaPush(property, propertySchema);
-                value[property] = this._getValidValueOrDefault(propertySchema, value[property], info);
+                const hasValue = Object.prototype.hasOwnProperty.call(value, property);
+                value[property] = this._getValidValueOrDefault(propertySchema, hasValue ? value[property] : void 0, info);
                 info.schemaPop();
                 info.valuePop();
             }