Batched state changes are not flushed if the promise code changes the DOM (= attaching an iframe). Reproduceable with Safari.

React version: 18.1.0

## Steps To Reproduce

1. Open [codepen](https://codepen.io/kh-viewar/pen/wvpVLxM) with Safari.
2. Click "Upload"
3. => "Spinner" text does not render while Promise is in pending

Link to code example:

https://codepen.io/kh-viewar/pen/wvpVLxM

## The current behavior

State changes are not executed.

## The expected behavior

State should change to true and render spinner component. After promise is resolved (2 seconds timeout), state should switch back to false and spinner component should unmount.

## Original discussion

https://github.com/facebook/react/issues/24365
if (
        existingCallbackNode == null &&
        existingCallbackPriority !== SyncLane
      ) {
        console.error(
          'Expected scheduled callback to exist. This error is likely caused by a bug in React. Please file an issue.',
        );
      }
    }
     
    return;
  }
  if (existingCallbackNode != null) {