long call dropped by system when 200 OK (UPDATE) is sent with SDP

What steps will reproduce the problem?
0. Both caller and callee supports 100rel.
1. Callee UA sends an UPDATE *with* SDP during call setup
2. Caller UA (Boghe/Doubango) responds with 200 OK *with* SDP
3. Call is setup successfully
4. After long time (about 15 minutes): IMS system sends an UPDATE *without* SDP
5. Caller UA (Boghe/Doubango) responds with 200 OK *with* SDP
6. IMS system sends BYE due to "Session released - Invalid SDP offer or answer"

What is the expected output? What do you see instead?
The client should respond with 200 OK *without* SDP, when receiving an UPDATE 
*without* SDP

What version of the product are you using? On what operating system?
boghe-r86 and doubango-r672 on Windows XP/Vista/7

Please provide any additional information below.
See RFC 3311.

Original issue reported on code.google.com by Jonne.K...@gmail.com on 30 Dec 2011 at 10:14

barchandune / doubango

long call dropped by system when 200 OK (UPDATE) is sent with SDP #90