`generateVerifyAndChangeEmailLink` only works for accounts with existing email

* Operating System version: Firebase Cloud
* Firebase SDK version: 12.6.0
* Firebase Product: auth
* Node.js version: 20
* NPM version: 10

#### Steps to reproduce:

In our app, we allow social login with Facebook (and more, but irrelevant). When authenticating with Facebook, the user can decide to not provide his email address. Since our whole application builds arounds mails, we ask them to provide one.

We activated email enumeration protection recently!

Since we can no longer set that mail in the frontend code and we want styled/custom mails, we would like to use `generateVerifyAndChangeEmailLink` in the admin library. But it seems impossible to call that function, if we don't provide an existing email.

This is, how the user looks in Firebase Console

#### Relevant Code:

```
// I tried different things for the existing mail, but all failed
await getAuth().generateVerifyAndChangeEmailLink('-', email, actionCodeSettings);
```