应用程序在WebCore上崩溃。在我们的应用程序中，我们在UIWebView上加载HTML5页面。当用户在UIWebView上导航到不同的屏幕时，应用程序会弹出警报弹窗，当用户单击“确定”按钮后，它会崩溃。
PS 注意：这个警报是HTML5警报，不是本地警报。
Thread 2 name: WebThread
Thread 2 Crashed:
0 JavaScriptCore 0x3570ec26 WTF::fastMalloc(unsigned long) + 870
1 WebCore 0x32cf731c WebCore::CSSSelectorList::adoptSelectorVector(WTF::Vector<WTF::OwnPtr<WebCore::CSSParserSelector>, 0ul>&) + 136
2 WebCore 0x32ceee10 cssyyparse(void*) + 848
3 WebCore 0x32de641a WebCore::CSSParser::parseSelector(WTF::String const&, WebCore::Document*, WebCore::CSSSelectorList&) + 74
4 WebCore 0x32de636e WebCore::Node::querySelectorAll(WTF::String const&, int&) + 90
5 WebCore 0x32de62a8 WebCore::jsElementPrototypeFunctionQuerySelectorAll(JSC::ExecState*) + 328
6 JavaScriptCore 0x35721592 JSC::Interpreter::privateExecute(JSC::Interpreter::ExecutionFlag, JSC::RegisterFile*, JSC::ExecState*) + 35526
7 JavaScriptCore 0x357a00e6 JSC::Interpreter::executeCall(JSC::ExecState*, JSC::JSObject*, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) + 1042
8 JavaScriptCore 0x3579fcca JSC::call(JSC::ExecState*, JSC::JSValue, JSC::CallType, JSC::CallData const&, JSC::JSValue, JSC::ArgList const&) + 46
9 WebCore 0x32e28cfc WebCore::JSEventListener::handleEvent(WebCore::ScriptExecutionContext*, WebCore::Event*) + 776
10 WebCore 0x32e289c0 WebCore::EventTarget::fireEventListeners(WebCore::Event*, WebCore::EventTargetData*, WTF::Vector<WebCore::RegisteredEventListener, 1ul>&) + 272
11 WebCore 0x32d2f36c WebCore::EventTarget::fireEventListeners(WebCore::Event*) + 136
12 WebCore 0x32d358de WebCore::Node::handleLocalEvents(WebCore::Event*) + 54
13 WebCore 0x32d3512e WebCore::EventDispatcher::dispatchEvent(WTF::PassRefPtr<WebCore::Event>) + 542
14 WebCore 0x32d34ee0 WebCore::EventDispatchMediator::dispatchEvent(WebCore::EventDispatcher*) const + 24
15 WebCore 0x32d34eb4 WebCore::EventDispatcher::dispatchEvent(WebCore::Node*, WebCore::EventDispatchMediator const&) + 92
16 WebCore 0x32d34e0c WebCore::Node::dispatchEvent(WTF::PassRefPtr<WebCore::Event>) + 28
17 WebCore 0x32d87eb8 WebCore::Document::finishedParsing() + 96
18 WebCore 0x32d87e50 WebCore::HTMLTreeBuilder::finished() + 16
19 WebCore 0x32d78fbe WebCore::HTMLDocumentParser::prepareToStopParsing() + 106
20 WebCore 0x32d78c9e WebCore::HTMLDocumentParser::finish() + 90
21 WebCore 0x32d78c3a WebCore::Document::finishParsing() + 14
22 WebCore 0x32d75e62 WebCore::DocumentWriter::endIfNotLoadingMainResource() + 74
23 WebCore 0x32d744fa WebCore::DocumentLoader::finishedLoading() + 74
24 WebCore 0x32dc19c8 WebCore::FrameLoader::finishedLoading() + 48
25 WebCore 0x32dc1938 WebCore::MainResourceLoader::didFinishLoading(double) + 88
26 WebCore 0x32dc18c2 _ZN7WebCoreL16didFinishLoadingEP16_CFURLConnectionPKv + 46
27 CFNetwork 0x371097ee URLConnectionClient::_clientDidFinishLoading(URLConnectionClient::ClientConnectionEventQueue*) + 186
28 CFNetwork 0x370fe49e URLConnectionClient::ClientConnectionEventQueue::processAllEventsAndConsumePayload(XConnectionEventInfo<XClientEvent, XClientEventParams>*, long) + 418
29 CFNetwork 0x370fe19c URLConnectionClient::processEvents() + 100
30 CFNetwork 0x370fe0d2 MultiplexerSource::perform() + 150
31 CoreFoundation 0x37445acc __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 8
32 CoreFoundation 0x37445298 __CFRunLoopDoSources0 + 208
33 CoreFoundation 0x3744403e __CFRunLoopRun + 646
34 CoreFoundation 0x373c749e CFRunLoopRunSpecific + 294
35 CoreFoundation 0x373c7366 CFRunLoopRunInMode + 98
36 WebCore 0x32d70c9c _ZL12RunWebThreadPv + 396
37 libsystem_c.dylib 0x33ce672e _pthread_start + 314
38 libsystem_c.dylib 0x33ce65e8 thread_start + 0
通过崩溃日志，很难确定确切的原因。请帮忙解决。