AI 143676: am: CL 143537 Sanity check to make sure the session still exists in auth_cb().
  BUG=1744549
  Original author: lockwood
  Merged from: //branches/cupcake/...

Automated import of CL 143676

diff --git a/utils/audio/avdtp.c b/utils/audio/avdtp.c
index 4710e66..12fc700 100644
--- a/utils/audio/avdtp.c
+++ b/utils/audio/avdtp.c

@@ -3000,6 +3000,11 @@
 	struct audio_device *dev;
 	GIOChannel *io;
 
+	if (!g_slist_find(sessions, session)) {
+		error("auth_cb called after session was freed");
+		return;
+	}
+
 	if (derr && dbus_error_is_set(derr)) {
 		error("Access denied: %s", derr->message);
 		if (dbus_error_has_name(derr, DBUS_ERROR_NO_REPLY)) {