Location.canonical_path: use empty host if host is None, see #8446

% borg repo-info
Location: rclone:///./pcloud:justtesting

src/borg/helpers/parseformat.py

@@ -619,7 +619,7 @@ class Location:
             return "{}://{}{}{}{}".format(
                 self.proto if self.proto else "???",
                 f"{self.user}@" if self.user else "",
-                self._host,  # needed for ipv6 addrs
+                self._host if self._host else "",  # needed for ipv6 addrs
                 f":{self.port}" if self.port else "",
                 path,
             )