Wizard spellbooks have a mechanic that binds the book to their first user, so other people can't use it. However, it binds the spellbook to the wizard's body, not their mind. This makes it so the spellbook is inaccessible to the wizard after becoming a lich or mindswapping, which doesn't seem to be intended. The PR just makes the spellbook check for the mind, not the body, to fix this. Fixes#64927 and #56216