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.
return <h1>{count}</h1>;
                }
              `,
            },
          ],
        },
      ],
    },
    {
      code: normalizeIndent`
        function Counter() {
          let [count, setCount] = useState(0);
          let [increment, setIncrement] = useState(0);
          useEffect(() => {
            let id = setInterval(() => {
              setCount(count + increment);
            }, 1000);
            return () => clearInterval(id);
          }, []);
          return <h1>{count}</h1>;
        }
      `,
      errors: [
        {
          message:
            "React Hook useEffect has missing dependencies: 'count' and 'increment'. " +
            'Either include them or remove the dependency array. ' +
            `You can also do a functional update 'setCount(c => ...)' if you ` +
            `only need 'count' in the 'setCount' call.`,
          suggestions: [