Allow email collection prompt even when userId is provided

The user wants to be able to collect an email address from a user in the chat widget even when a `userId` is already being passed in the Messenger's boot function. Currently, providing a `userId` prevents the chat from prompting for an email, forcing a choice between identifying the user by `userId` (for account/company context) and collecting their email. The desired behavior is to allow both: identify the user with `userId` and still prompt for an email if it's not already known, without losing the existing account/company context. This would enable more flexible lead capture and user identification.