Use bump order when index sort type is unrecognized instead of throwing an error.

src/General/Index.coffee

@@ -763,6 +763,7 @@ Index =
       when 'birth'      then [liveThreadIDs... ].sort (a, b) -> b - a
       when 'replycount' then [liveThreadData...].sort((a, b) -> b.replies - a.replies).map (post) -> post.no
       when 'filecount'  then [liveThreadData...].sort((a, b) -> b.images  - a.images ).map (post) -> post.no
+      else liveThreadIDs
     if Index.search and (threadIDs = Index.querySearch Index.search)
       Index.sortedThreadIDs = threadIDs
     # Sticky threads