Segfault in `base::SequenceCheckerImpl::CalledOnValidSequence()`.

Seen [in this CI run](https://app.circleci.com/pipelines/github/electron/electron/32652/workflows/d9f0c307-7021-453d-8bec-6b2eb9bd2bc2/jobs/718582). 

```
Received signal 11 <unknown> 000000000000
0   Electron Framework                  0x000000011ab9ece9 base::debug::CollectStackTrace(void**, unsigned long) + 9
1   Electron Framework                  0x000000011aa931e3 base::debug::StackTrace::StackTrace() + 19
2   Electron Framework                  0x000000011ab9ebb1 base::debug::(anonymous namespace)::StackDumpSignalHandler(int, __siginfo*, void*) + 2385
3   libsystem_platform.dylib            0x00007fff68b8c5fd _sigtramp + 29
4   ???                                 0x0000000000000000 0x0 + 0
5   Electron Framework                  0x000000011ab09bda base::SequenceCheckerImpl::CalledOnValidSequence() const + 42
6   Electron Framework                  0x000000011ab25bd9 base::SupportsUserData::GetUserData(void const*) const + 25
7   Electron Framework                  0x000000011526f1d2 electron::api::WebContents::DidStopLoading() + 50
8   Electron Framework                  0x0000000119bc2401 content::WebContentsImpl::LoadingStateChanged(bool, content::LoadNotificationDetails*) + 2049
9   Electron Framework                  0x0000000119bcab12 content::WebContentsImpl::DidStopLoading() + 178
10  Electron Framework                  0x000000011983fcc8 content::FrameTreeNode::DidStopLoading() + 120
11  Electron Framework                  0x0000000119937cd5 content::RenderFrameHostImpl::DidStopLoading() + 133
12  Electron Framework                  0x0000000116b3d1fa content::mojom::FrameHostStubDispatch::Accept(content::mojom::FrameHost*, mojo::Message*) + 3610
13  Electron Framework                  0x000000011b058953 mojo::InterfaceEndpointClient::HandleValidatedMessage(mojo::Message*) + 931
14  Electron Framework                  0x000000011b05c62f mojo::MessageDispatcher::Accept(mojo::Message*) + 191
15  Electron Framework                  0x000000011b059e71 mojo::InterfaceEndpointClient::HandleIncomingMessage(mojo::Message*) + 97
16  Electron Framework                  0x000000011b0b8132 IPC::(anonymous namespace)::ChannelAssociatedGroupController::AcceptOnProxyThread(mojo::Message) + 706
17  Electron Framework                  0x000000011b0b4f8c base::internal::Invoker<base::internal::BindState<void (IPC::(anonymous namespace)::ChannelAssociatedGroupController::*)(mojo::Message), scoped_refptr<IPC::(anonymous namespace)::ChannelAssociatedGroupController>, mojo::Message>, void ()>::RunOnce(base::internal::BindStateBase*) + 140
18  Electron Framework                  0x000000011ab2e20b base::TaskAnnotator::RunTask(char const*, base::PendingTask*) + 395
19  Electron Framework                  0x000000011ab4d1b0 base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWorkImpl(base::sequence_manager::LazyNow*) + 528
20  Electron Framework                  0x000000011ab4ce08 base::sequence_manager::internal::ThreadControllerWithMessagePumpImpl::DoWork() + 168
21  Electron Framework                  0x000000011abbede1 base::MessagePumpCFRunLoopBase::RunWork() + 65
22  Electron Framework                  0x000000011abb4162 base::mac::CallWithEHFrame(void () block_pointer) + 10
23  Electron Framework                  0x000000011abbe7af base::MessagePumpCFRunLoopBase::RunWorkSource(v
```
shell/browser/api/electron_api_web_contents.cc
const std::string& channel,
                              blink::CloneableMessage arguments,
                              MessageSyncCallback callback) {
  TRACE_EVENT1("electron", "WebContents::MessageSync", "channel", channel);
   webContents.emit('-ipc-message-sync', new Event(sender, message), internal,
   channel, arguments);
  EmitWithSender("-ipc-message-sync", receivers_.current_context(),
                 std::move(callback), internal, channel, std::move(arguments));
}
void WebContents::MessageTo(bool internal,
                            bool send_to_all,
                            int32_t ontents_id,
                            const std::string& channel,
                            blink::CloneableMessage arguments) {
  TRACE_EVENT1("electron", "WebContents::MessageTo", "channel", channel);
  auto* ontents = FromID(ontents_id);
  if (ontents) {
    ontents->SendIPCMessageWithSender(internal, send_to_all, channel,
                                           std::move(arguments), ID());
  }
}
void WebContents::MessageHost(const std::string& channel,