wp_update_user() - PHP notice when ID not specified.

[tyxla]

When using wp_update_user() with no ID specified, a WP_Error is thrown, indicating : Invalid User ID..

This is fine, however, a notice for invalid $userdata array key ID is still being thrown as well.

This appears to be a really old issue - I was able to encounter it in 3.1.

[tyxla]

Related: #23005, #25745, #16731, #17009

[tyxla]

Making sure that ID is set before using it.

[SergeyBiryukov]

[31269] missed the ticket.