XWIKI-10814: "create document" form: add links if the document already e...

...xist
$DocAlreadyExistsRef is a DocumentReference already since you just created it, when you do "$DocAlreadyExistsRef" you concert it to String and end up using XWiki#getURL(String fullname, String action) that will have to parse the String to create a DocumentReference again. You should pass directly the $DocAlreadyExistsRef.