Confounding example on `MonadError.handleError`

[yhpark]

In Ch. 4.5.2, the book shows a simple example of using handleError method, which maps the error type String to ErrorOr[String] so the resulting type is nested ErrorOr[ErrorOr[String]] which possibly confound readers to think handleError takes E => F[A]. I would change the example to handleError returns some Int instead of ErrorOr[String] because it's simpler and coherent with the previous code example.

[yhpark]

Also I found the exercise 4.5.4 Exercise: Abstracting empty. Seems it's been left unfinished since the initial writing 3 years ago

[noelwelsh]

Thanks. I've fixed it now.