fix incorrect handling of required fields

toREST/include/torrent.hpp

@@ -142,7 +142,7 @@ void patch(torrent_session &session, response resp, request req) {
     torrent.set_download_limit(down_limit);
   }
 
-  if (down_limit_field || up_limit_field || paused_field) {
+  if (!down_limit_field && !up_limit_field && !paused_field) {
     return respond(http::bad_request);
   }