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.
const codeLines = strings[0].split('\n');
  const leftPadding = codeLines[1].match(/\s+/)[0];
  return codeLines.map(line => line.substr(leftPadding.length)).join('\n');
}
const tests = {
  valid: [
    {
      code: normalizeIndent`
        function MyComponent() {
          const local = {};
          useEffect(() => {
            console.log(local);
          });
        }
      `,
    },
    {
      code: normalizeIndent`
        function MyComponent() {
          useEffect(() => {
            const local = {};
            console.log(local);