[CAL-3696] disable default confirmation emails for attendees cannot be undone and breaks page

[PeerRich]

test it here: cal.com/ghldirect

_{From SyncLinear.com | CAL-3696}

[GaryGHL]

To add, the form works fine on creation until the option above is selected. This then causes the error on submission, sometimes the booking is made, sometimes not. The redirect or confirmation page never shows. Unchecking the option doesn't resolve, only fix is to delete the event type and recreate without checking the attended email box, if you do, the error returns.

[emrysal]

Having issues reproducing this issue on local but managed to reproduce on @GaryGHL's profile. Not the disable default for attendees though but managed to make it crash on the disable default for host. Looking into this more (as the error is not even making it to Sentry!)