tools,doc: apilinks should handle root scenarios

* Prevent crash when setting root properties
* Allow return outside of function

PR-URL: https://github.com/nodejs/node/pull/22721


Reviewed-By: Sam Ruby <rubys@intertwingly.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>