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 def = resolved.defs[0];
                      if (def != null && def.type === 'Parameter') {
                        setStateRecommendation = {
                          missingDep,
                          setter: maybeCall.callee.name,
                          form: 'inlineReducer',
                        };
                      }
                    }
                  }
                  break;
                }
              }
              maybeCall = maybeCall.parent;
            }
            if (setStateRecommendation !== null) {
              break;
            }
          }
        });
        if (setStateRecommendation !== null) {
          switch (setStateRecommendation.form) {
            case 'reducer':
              extraWarning =
                ` You can also replace multiple useState variables with useReducer ` +
                `if '${setStateRecommendation.setter}' needs the ` +
                `current value of '${setStateRecommendation.missingDep}'.`;