A page with a slash ("/", %2F) in its name cannot be inline-edited

Steps to reproduce : 

• Start with a fresh instance
• In the administration, remove the naming strategy that removes "/" from page name
• Create a page with a slash in its name
• Try to edit the page

Expected : the WYSIWYG inline editor pops up

Actual :

• The user gets a message saying that XWiki is unable to load the page
• The result of the ajax call to /xwiki/rest/..../spaces/xxxxxx/?timestamp=xxxxxxx that is made to get the content of the document returns "Malformed URL: the spaces section is invalid."

Note : Even though we do have a naming strategy to prevent new pages from having this special character in their name, there are multiple situations in which a standard user could get the issue : 

• Either it’s a long-lived page that has been there in previous versions of the wiki, and suddenly the page stops being easily editable because the wiki has been upgraded
• Or it’s a page that has been imported from a 3rd party platform, which does not enforce any rules for page names