Subtle URL breaking regression in 5.1sp1 and later

This is probably only a problem in edge cases involving custom code, but posting it here in case it saves anyone some frustration.

In Sitefinity 5.0 SP1 and earlier, "split" pages (as opposed to pages that are "synchronized between translations") that had different URLs in different languages could be accessed by either name. That is, if you had a page with EN url name "split" and DE url name "split-de", /en/split and /en/split-de both go to the English version of that page, and /de/split and /de/split-de both go to the German version of the page. In Sitefinity 5.1 SP1 and later, this is no longer true; /en/split-de and /de/split both 404. Sitefinity never generated links to those non-standard URLs, so this is unlikely to break peoples bookmarks. (If it is a problem for you, just add the URL that used to work as an alternate URL in the "Title and Properties" screen.)

Note that all URLs still work for synchronized translations (as of 5.2 SP1) - if you have EN page with url name "sync" and synchronized DE translation with url name "sync-de", /en/sync and /en/sync-de both go to the English version and /de/sync and /de/sync-de go to the German version.