We can use gst_uri_from_string_with_base () to join base url and the fragment url path. The previous method of forming base url in update_base_url(), by looking for the string 'manifest' or 'Manifest' is insufficient. A query may include these string in their paths and thus an invalid base url string will be kept. Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8193>