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) {
          let [, setState] = useState();
          let taint = props.foo;
          function handleNext(value) {
            let value2 = value * taint;
            setState(value2);
            console.log('hello');
          }
          useEffect(() => {
            return Store.subscribe(handleNext);
          }, [handleNext]);
        }
      `,
      errors: [
        {
          message:
            `The 'handleNext' function makes the dependencies of ` +
            `useEffect Hook (at line 14) change on every render. ` +
            `Move it inside the useEffect callback. Alternatively, wrap the ` +
            `definition of 'handleNext' in its own useCallback() Hook.`,
          suggestions: undefined,
        },
      ],
    },
    {
      code: normalizeIndent`