web-api: type-safe response properties access

What type of issue is this? (place an x in one of the [ ])

• bug

Requirements (place an x in each of the [ ])

• I've read and understood the Contributing guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've searched for any related issues and avoided creating a duplicate issue.

Bug Report

const slackUser = await app.client.users.info({
    user: installation.user.id,
})

slackUser.user.name // Object `user` is possibly 'undefined'.

If there was an error here, the function would throw an error and we could catch it somewhere else. It's confusing me and should be a bug that we can't safely access properties after a function is called with no errors.

Should we be having to use if {} else {} to safely access these properties?

Reproducible in:

package version: "@slack/bolt": "^3.12.2",

Reproduce the TypeScript example from the report using @slack/bolt 3.12.2, then trace the response type for app.client.users.info and its user property. Done means a successful response can expose its properties without an unnecessary undefined check, with coverage for the reported access pattern.