fix issue415

[Routee]

!Issue 415

[knaeckeKami]

Hi!

Thanks for you PR.

The GraphQL spec actually required every error to have a String message, see

https://spec.graphql.org/October2021/#sec-Errors.Error-result-format

So I think throwing an Exception is the right behaviour, even though the Exception could be more descriptive I admit.

If you want non-standard behavior like this, you can pass your own ResponseParser to your HttpLink/DioLink.