Fix torrent name being blank when root folder is renamed to /

Update changelog (for previous commit as well)

deluge/core/torrent.py

@@ -608,6 +608,8 @@ class Torrent:
         def ti_name():
             if self.handle.has_metadata():
                 name = self.torrent_info.file_at(0).path.split("/", 1)[0]
+                if not name:
+                    return self.torrent_info.name()
                 try:
                     return name.decode("utf8", "ignore")
                 except UnicodeDecodeError: