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() {
          const ref = useRef();
          const [state, setState] = useState();
          useEffect(() => {
            ref.current = {};
            setState(state + 1);
          }, [ref]);
        }
      `,
      errors: [
        {
          message:
            "React Hook useEffect has a missing dependency: 'state'. " +
            'Either include it or remove the dependency array. ' +
            `You can also do a functional update 'setState(s => ...)' ` +
            `if you only need 'state' in the 'setState' call.`,
          
          
          
          suggestions: [
            {
              desc: 'Update the dependencies array to be: [ref, state]',
              output: normalizeIndent`
                function MyComponent() {