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.
function Thing() {
          useEffect(async () => {});
        }
      `,
      errors: [
        {
          message:
            `Effect callbacks are synchronous to prevent race conditions. ` +
            `Put the async function inside:\n\n` +
            'useEffect(() => {\n' +
            '  async function fetchData() {\n' +
            '    // You can await here\n' +
            '    const response = await MyAPI.getData(someId);\n' +
            '    // ...\n' +
            '  }\n' +
            '  fetchData();\n' +
            `}, [someId]); // Or [] if effect doesn't need props or state\n\n` +
            'Learn more about data fetching with Hooks: https://reactjs.org/link/hooks-data-fetching',
          suggestions: undefined,
        },
      ],
    },
    {
      code: normalizeIndent`
        function Example() {
          const foo = useCallback(() => {
            foo();
          }, [foo]);
        }
      `,