Adding a personal workspace's owner to a repo shows an error

Issue Summary

Inviting the owner of a personal workspace to one of the workspace's repos gives an error.

The owner of a personal workspace gains automatically access to any workspace repositories, so an invitation is not needed in this case.
However, this access is not displayed in workspace's Settings, please see BCLOUD-21334.

If the owner thinks they don't have access and they try to add their user to a repo, they get an error.

Steps to Reproduce

1. Create a new Bitbucket Cloud account
2. Create a new repository that is owned by the personal workspace created automatically for this Bitbucket Cloud account
3. Go to this repository's Settings > User and group access
4. Select Add members
5. Type the email of the Bitbucket Cloud account that is owner of the workspace, select any type of access, and then Confirm

Expected Results

A message that says this user already has access to this repository.

Actual Results

An error is shown, with the message

Issue adding new user
The following user could not be added by email: "<email>". Try again.

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available