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.
suggestions: undefined,
        },
      ],
    },
    {
      code: normalizeIndent`
        function MyComponent(props) {
          function handleNext1() {
            console.log('hello');
          }
          const handleNext2 = () => {
            console.log('hello');
          };
          let handleNext3 = function() {
            console.log('hello');
          };
          useEffect(() => {
            handleNext1();
            return Store.subscribe(() => handleNext1());
          }, [handleNext1]);
          useLayoutEffect(() => {
            handleNext2();
            return Store.subscribe(() => handleNext2());
          }, [handleNext2]);
          useMemo(() => {
            handleNext3();
            return Store.subscribe(() => handleNext3());
          }, [handleNext3]);
          return (
            <div