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.
/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */
'use strict';
const ESLintTester = require('eslint').RuleTester;
const ReactHooksESLintPlugin = require('eslint-plugin-react-hooks');
const ReactHooksESLintRule = ReactHooksESLintPlugin.rules['exhaustive-deps'];
/**
 * A string template tag that removes padding from the left side of multi-line strings
 * @param {Array} strings array of code strings (only one expected)
 */
function normalizeIndent(strings) {