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.
stableKnownValueCache,
      );
      const memoizedIsFunctionWithoutCapturedValues = memoizeWithWeakMap(
        isFunctionWithoutCapturedValues,
        functionWithoutCapturedValueCache,
      );
      
      const currentRefsInEffectCleanup = new Map();
      
      
      
      function isInsideEffectCleanup(reference) {
        let curScope = reference.from;
        let isInReturnedFunction = false;
        while (curScope.block !== node) {
          if (curScope.type === 'function') {
            isInReturnedFunction =
              curScope.block.parent != null &&
              curScope.block.parent.type === 'ReturnStatement';
          }
          curScope = curScope.upper;
        }
        return isInReturnedFunction;
      }
      
      
      const dependencies = new Map();
      const optionalChains = new Map();
      gatherDependenciesRecursively(scope);
      function gatherDependenciesRecursively(currentScope) {