Non existing pages can be rated

Steps to reproduce: 

• install Rating Application if XWiki doesn't have it
• Type in the URL a non-existing page
• Vote the page

Expected results:

• Non existing page can't be voted

Actual results:

• The page can be voted:
  

• The page is created and has a vote.
  The issue is that the page is created with "XWikiGuest" author, instead of the actual user that created the page.