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 Hello({ prop1, prop2 }) {
          const [state, setState] = useState(0);
          useEffect(() => {
            if (prop1) {
              setState(prop2);
            }
          });
        }
      `,
      errors: [
        {
          message:
            `React Hook useEffect contains a call to 'setState'. ` +
            `Without a list of dependencies, this can lead to an infinite chain of updates. ` +
            `To fix this, pass [prop1, prop2] as a second argument to the useEffect Hook.`,
          suggestions: [
            {
              desc: 'Add dependencies array: [prop1, prop2]',
              output: normalizeIndent`
                function Hello({ prop1, prop2 }) {
                  const [state, setState] = useState(0);
                  useEffect(() => {
                    if (prop1) {
                      setState(prop2);
                    }
                  }, [prop1, prop2]);
                }
              `,
            },