1/ Import the attached page in an XWiki 5.4.6 with an office server configured
2/ an infinite loading sign will appear on the page in the office viewer and the presentation will never be visible
3/ rename the page, remove all the whitespaces in the name
4/ on the renamed page the office viewer will work just fine.
Note that the issue is not only for the whitespaces, but seems to be for all special characters from an URL point of view (those that would be encoded in an URL).
I am marking this as a regression as this used to work on 5.2.1 (import the same page on a 5.2.1, it will work).