Kit crashes if an error is thrown from an async function

[joelanman]

Description of the issue

If an error is thrown in an async function, the kit crashes

Steps to reproduce the issue

a route like this will crash:

router.get("/test", async (req, res) => {
  functionDoesNotExist()
})

Actual vs expected behaviour

The kit should catch the error and show an error page as it does with other errors

[joelanman]

a workaround is to add an error handler to the async function, for example using this module: https://www.npmjs.com/package/express-async-handler