IndexedDB: Result of failed request should be |undefined|

LayoutTests/storage/indexeddb/mozilla/resources/add-twice-failure.js

 // original test:
 // http://mxr.mozilla.org/mozilla2.0/source/dom/indexedDB/test/test_add_twice_failure.html
 // license of original test:
 // " Any copyright is dedicated to the Public Domain.
 //   http://creativecommons.org/publicdomain/zero/1.0/ "
 
 if (this.importScripts) {
     importScripts('../../../../resources/js-test.js');
     importScripts('../../resources/shared.js');
 }
@@ skipping 16 matching lines @@
 function addFirstSuccess()
 {
     shouldBe("request.result", "key");
     request = evalAndLog("request = objectStore.add({}, key);");
     request.onsuccess = unexpectedSuccessCallback;
     request.onerror = addSecondExpectedError;
 }
 
 function addSecondExpectedError()
 {
+    shouldBeUndefined("event.target.result");
+    shouldBeNonNull("event.target.error");
     shouldBe("event.target.error.name", "'ConstraintError'");
     event.preventDefault();
     finishJSTest();
 }