[TRI-1133] The React hook useEventRunDetails should accept string | undefined

[matt-aitken]

It should work but the TypeScript type is incorrect in the params.

Steps

1. Change the eventId type in packages/react/src/events.ts to be string | undefined. Do not use an optional as we want to force people to put a value here.
2. Test this by modifying the examples/nextjs-example to have an undefined when it uses the hook

_TRI-1133