do not overwrite the error stack in json parser

[bjohansebas]

This is just a reminder that we need to stop overwriting the stack, and use error.cause or something similar.

Discovered in #604

[wesleytodd]

error.cause! Also, often in cases like this the stack can be pretty unhelpful to end users, so you can use Error.captureStackTrace in some cases to help make more clear traces back into user code.