Preview does not work for translated documents if the page does not exist at all

There is no error (at least provided XWIKI-23464 is fixed or you are testing before 11.5) but since the page does not exist the UI indicate that the page does not exist before even trying to display the translation.

Unfortunately, translations are mostly unusable in XWiki without the corresponding default version, so it might be hard to fix. It's possible to "fix" is to disable the access to the preview in such a case.