<!--
  Please provide a clear and concise description of what the bug is. Include
  screenshots if needed. Please test using the latest version of the relevant
  React packages to make sure your issue has not already been fixed.
-->

React version: v16

## Steps To Reproduce

```js
import React from "react";

export const Q = React.memo(() => {});
export const Z = React.forwardRef(() => {});

export default function App() {
  return (
    <>
      <Q />
      <Z />
    </>
  );
}
```

Link to code example: https://codesandbox.io/s/hoc-throw-null-xrhwg

## The current behavior

No errors.

## The expected behavior

> Nothing was returned from render. This usually means a return statement is missing. Or, to render nothing, return null.
invariant(
      typeof iteratorFn === 'function',
      'An object is not an iterable. This error is likely caused by a bug in ' +
        'React. Please file an issue.',
    );
    if (__DEV__) {
      // 
      // 
      if (
        typeof Symbol === 'function' &&
        // 
        newChildrenIterable[Symbol.toStringTag] === 'Generator'
      ) {
        if (!didWarnAboutGenerators) {
          console.error(
            'Using Generators as children is unsupported and will likely yield ' +
              'unexpected results because enumerating a generator mutates it. ' +
              'You may convert it to an array with `Array.from()` or the ' +
              '`[...spread]` operator before rendering. Keep in mind ' +
              'you might need to polyfill these features for older browsers.',
          );
        }
        didWarnAboutGenerators = true;
      }
      // 
      if ((newChildrenIterable: any).entries === iteratorFn) {
        if (!didWarnAboutMaps) {
          console.error(
            'Using Maps as children is not supported. ' +
              'Use an array of keyed ReactElements instead.',