Assertion when incoming reoffer SDP contains no media (thanks Ashraf Jaddo for the report)

[nanang]

Original report can be found ​here.

I am using PJSIP 1.12 with iPhone 5.0.. I am getting “Assertion
failed: (sdp_remote && m_rem), function transport_encode_sdp, file
../src/pjmedia/transport_srtp.c, line 1299.” every time I try to
call certain numbers..
...
the problem is when I call from iPhone to a PBX extension that is
connected to the service.. and I I get the above error, to be specific
the code crash only when I pick up the call from that extension..

Snippet log:
...
(normal outgoing initial INVITE until ACK ..)
...
15:31:31.393   pjsua_core.c  RX 703 bytes Request msg UPDATE/cseq=102
 (rdata0x9061bc) from tcp 10.50.0.4:5060:
UPDATE sip:77999991@10.50.1.10:5060;transport=TCP;ob SIP/2.0
Via: SIP/2.0/TCP 10.50.0.4:5060;branch=z9hG4bK4b370dd7;rport
Max-Forwards: 70
From: sip:9874@10.50.0.4;tag=as5a9c25b2
To: sip:77999991@10.50.0.4;tag=PxbkZXr7smjwglhT87678rIypjrr0tln
Contact: <sip:9874@10.50.0.4:5060;transport=TCP>
Call-ID: F3a8f5vZu0f6JEJFmlN5vIagy-P1De7h
CSeq: 102 UPDATE
User-Agent: TEST
Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, SUBSCRIBE, 
 NOTIFY, INFO, PUBLISH
Supported: replaces, timer
X-asterisk-Info: SIP re-invite (External RTP bridge)
Content-Type: application/sdp
Content-Length: 102
 
v=0
o=root 2007926168 2007926170 IN IP4 172.16.201.225
s=TEST
c=IN IP4 172.16.201.225
t=0 0

Such reoffer should be just simply rejected and any existing session won't get updated.

[nanang]

(In [3962]) Fix #1457: removed check for remote SDP media count before calling find_audio_index() in pjsua_media_channel_create_sdp(), so find_audio_index() will also verify the media count in the remote SDP.