eslint-plugin-react-hooks version: 4.2.0

## Steps To Reproduce

I know it shouldn't exist in production code, but it's annoying while editing some files.

```js
import React, { useEffect } from "react";

const App = () => {
  useEffect(); // <-
  return null;
};

export default App;
```

Link to code example: https://codesandbox.io/s/polished-sun-3wr27?file=/src/App.js

## The current behavior

ESLint crashed.

```
TypeError: Cannot read property 'type' of undefined
```

## The expected behavior

ESLint doesn't crash but reports an error instead.
},
      ],
    },
    {
      code: normalizeIndent`
        function MyComponent(props) {
          const ref1 = useRef();
          const ref2 = useRef();
          useEffect(() => {
            ref1?.current?.focus();
            console.log(ref2?.current?.textContent);
            alert(props.someOtherRefs.current.innerHTML);
            fetch(props.color);
          }, [ref1?.current, ref2?.current, props.someOtherRefs, props.color]);
        }
      `,
      errors: [
        {
          message:
            "React Hook useEffect has unnecessary dependencies: 'ref1.current' and 'ref2.current'. " +
            'Either exclude them or remove the dependency array. ' +
            "Mutable values like 'ref1.current' aren't valid dependencies " +
            "because mutating them doesn't re-render the component.",
          suggestions: [
            {
              desc:
                'Update the dependencies array to be: [props.someOtherRefs, props.color]',
              output: normalizeIndent`
                function MyComponent(props) {
                  const ref1 = useRef();