Fix a bug that the confirmation dialog for a new mail doesn't work

[HashidaTKS]

On a new mail, data.originalRecipients.to is undefined, and data.originalRecipients.to.map(...) raises an invalid member access error. We need to check if to is undefined or not.
You need to check cc and bcc as well.

• Confirm that the confirmation dialog for new mail work fine.
• Confirm that the warning for newly added domains are worked fine.

[piroor]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Nullish_coalescing
These operatiors require Chrome/Edge 80 and later which was released at 2020. Windows 10 LTSB released at 2016 is still alive until 2026, so such very old environments need to be dropped with this change. Anyway such versions are not recommended to use with public Internet, thus it looks reasonable to drop them.

[HashidaTKS]

https://babeljs.io/docs/babel-plugin-transform-nullish-coalescing-operator

This plugin is included in @babel/preset-env, in ES2020

Our babel.config.json:

{
  "presets": ["@babel/preset-env"]
}

So I think webpacked(compiled) source codes are transpilied to not use .? and ??.
Actually, webpacked(compiled) confirm.js does not contain .? and ??.