If tmpl is NULL name is not free.
so we need to fix as below.

  /* TODO use stream's name/bitrate/index as the pad name? */
  if (streamtype == MSS_STREAM_TYPE_VIDEO) {
    name = g_strdup_printf ("video_%02u", mssdemux->n_videos++);
    tmpl = gst_static_pad_template_get (&gst_mss_demux_videosrc_template);
  } else if (streamtype == MSS_STREAM_TYPE_AUDIO) {
    name = g_strdup_printf ("audio_%02u", mssdemux->n_audios++);
    tmpl = gst_static_pad_template_get (&gst_mss_demux_audiosrc_template);
  }

  if (tmpl != NULL) {
    srcpad = GST_PAD_CAST (gst_pad_new_from_template (tmpl, name));
-   g_free (name)
    gst_object_unref (tmpl);
  }
+  g_free (name);