Occurs in Fiber with multiple instances of the React package (which can't share current owner).
if (maybeIterable === null || typeof maybeIterable === 'undefined') {
    return null;
  }
  const iteratorFn =
    (ITERATOR_SYMBOL && maybeIterable[ITERATOR_SYMBOL]) ||
    maybeIterable[FAUX_ITERATOR_SYMBOL];
  if (typeof iteratorFn === 'function') {
    return iteratorFn;
  }
  return null;
}
function coerceRef(current: Fiber | null, element: ReactElement) {
  let mixedRef = element.ref;
  if (mixedRef !== null && typeof mixedRef !== 'function') {
    if (element._owner) {
      const owner: ?(Fiber | ReactInstance) = (element._owner: any);
      let inst;
      if (owner) {
        if (typeof owner.tag === 'number') {
          const ownerFiber = ((owner: any): Fiber);
          invariant(
            ownerFiber.tag === ClassComponent,
            'Stateless function components cannot have refs.',
          );
          inst = ownerFiber.stateNode;
        } else {
          
          inst = (owner: any).getPublicInstance();
        }
      }